Military Forum for Russian and Global Defence Issues


    Future of Russian IFV/BMPT

    Share
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Mon Jan 29, 2018 12:41 pm

    So is the recoil force stated by Tulamash the recoil force of the gun, or the recoil force on the turret? As you said before, the recoil force of a gun like the 2A42 is 40-50 kN, but it gets reduced by the muzzle brake to 30-40 kN and the turret receives 30-40 kN. If that is the case, then the given recoil force from the website must be pure recoil of the gun without considering any other factors, like the nonsense that you spouted. How does your logic fit that in? You can't, because it's nonsensical and self-contradictory.

    I will believe in your sources when you show them.

    As for the accuracy (and lethality) of 2A72, this graph may be interesting. It is aimed at showing the advantages of the BMP-1M with the "Kliver" turret compared to a regular BMP-1. Graph taken from БМП-1 (1964-2000) by Sergey Malyshev.



    Graph on the right shows the probability of destroying a generic APC with 16 rounds from the 30mm AP (autocannon) when firing from a stationary position and when firing on the move compared to 2 shots from the 73mm cannon of the BMP-1. The distance where the probability of destroying an APC with 16 rounds from a 2A72 cannon is practically guaranteed (0.8) is 1.2 km when firing from a stationary position and 1.0 km when firing on the move. Probability of destroying an APC with the "Grom" 73mm cannon with 2 shots at 500 meters is 0.8, which is why 500 m is considered the effective range of the cannon. This might be useful to someone.
    avatar
    GarryB

    Posts : 17213
    Points : 17819
    Join date : 2010-03-30
    Location : New Zealand

    Re: Future of Russian IFV/BMPT

    Post  GarryB on Mon Jan 29, 2018 10:36 pm

    The first thing: 2A38 is double barrel gun and fire barrel by barrel. Obviously the two barrel's axis are located either on the left or on the right of gun's axis. This makes the recoil stronger on the gun's axis. The same situation may happen with the 6-barrel 30mm guns like gsh-630, etc.

    Recoil is important if it is too much for the platform it is mounted on... for a vehicle however most IFVs these days are well over 15 tons so 5 tons of recoil is not that big a deal.

    the twin barrel 30mm 2A38M is more accurate than their 6 barrel gatlings... fixed barrels are more accurate than revolving ones, though revolving barrels can often have each barrel offset to improve or reduce accuracy.

    A shotgun is effective because it delivers lots of projectiles around the point of aim so if the target changes path after the shot is fired and before the rounds impact there is still a good chance of hits against small fast targets.


    1. The long-recoil operated gun like 2A72 push far less recoil on the gun mounting than gas-operated gun like 2A42.

    Guns with similar barrel lengths firing the same ammo have the same recoil energy.

    A gas operated rifle has less felt recoil than a bolt action, and a long recoil operated SMG has even less felt recoil because the energy is spread over a longer period.

    All of this is important if you are shoulder firing the weapon but a fixed mount in a recoil absorbing system and it really does not matter at all.

    4. I have the points to suggest replacing 2A42 guns by 2A72 guns on new version of BMPT . The first, 2A72 is far less recoil so will make the turret less vibration, especiall when the guns are highly mounted (like on BMPT-72) and the accuracy will be improved finally. The second, if they can improve the feeding limitation (on BMPT-72) to feed both type of rounds on each gun, they can select what round they want and fire it simultaneously at maximum 1,100 rpm, enough to deal with all of its assigned targets. The third, it is cheaper to acquire and maintain the 2A72 guns.

    The choice of the 2A42 was always a compromise... it is heavy but reliable, but most importantly it is cheap.

    Considering the vehicle it is actually replacing in the ground troop fire support role is actually the Tunguska and Shilka I personally think replacing the two single barrel guns with a single 2A38M cannon makes rather more sense with a rate of fire reduction and burst limiter... I mean if they are firing from fixed belts anyway why not use a weapon with a higher rate of fire in short bursts... it would also be more effective against aircraft.

    I rather suspect in the near future the combination of high velocity 57mm guns and 57mm grenade launchers will largely replace the 30mm weapons and 40mm grenade launchers will totally replace the 30mm weapons in service now.


    _________________
    “The West won the world not by the superiority of its ideas or values or religion […] but rather by its superiority in applying organized violence. Westerners often forget this fact; non-Westerners never do.”

    ― Samuel P. Huntington, The Clash of Civilizations and the Remaking of World Order

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Tue Jan 30, 2018 3:06 am

    I agree that they can install 2A42 gun on light combat wheeled vehicles like BTR-82A, BTR-4, Uran-9, Tiger-M but with the trade-off of firing accuracy. If they want to keep the firing accuracy while on stop and while on move, they will have to reinforce gun mounting, turret, hull and chassis. In that case, the vehicles will gain a significant weight that may ask for changing engine, reducing the protection level, etc.
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Tue Jan 30, 2018 3:33 am

    less felt recoil because the energy is spread over a longer period.

    Just a minor correction, Garry. Technically speaking, felt recoil is not really about energy as in kinetic energy, but about momentum. That's why recoil force is expressed as a force, in Newtons, and not as energy, in Joules.

    Also, about the "HE vs wall" thing, here's what 30x165mm HE shells do to walls, at least when they are fired out of a Finnish BMP-2, according to an ex-BMP-2 mechanic posting on Reddit.

    Well since it's my first ever post on reddit I have no clue about what I'm doing here, but this is an album I compiled from my time in the Finnish Defence Forces as a BMP-2 mechanic. Actually seeing what these suckers really did to targets gave me a new respect for the 30mm cannon the BMP-2 has.

    Here's his imgur album: https://imgur.com/a/zBP1K

    10cm concrete brick wall reinforced with rebar:



    The back of the wall:



    Last edited by Interlinked on Thu Feb 08, 2018 9:06 am; edited 1 time in total

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Tue Jan 30, 2018 7:36 am

    Comparison with the gun 2A42:

    The 2A72 cannon, due to the use of a moving barrel scheme, transfers to the roof of the armored object a more extended recoil momentum, which means it has a smaller maximum recoil force, which makes it possible to use it on light armored vehicles such as BTR-82, Tigr- M with armored corps made of sheets with a thickness of only about 7mm, on which the use of armament more powerful than the 14.5 mm KPVT machine gun before the appearance of the 30mm gun 2A72 was previously impossible. This puts them on the same level as the heavier and more expensive infantry combat vehicles and significantly increases the combat value of light armored vehicles in defense (when the battle is fought from the trench and the level of armor protection of the combat vehicle is not so important).

    The fee for using the scheme with a movable barrel was a somewhat worse accuracy and a much smaller rate of fire - only 300-330 rds / min, which makes it impossible to effectively use this gun for air targets.

    http://www.history147.ru/2017/09/blog-post.html?m=1

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Tue Jan 30, 2018 11:09 am

    Just looked back the Newton formula to calculate how much force needed to stop the barrel of 2A72 gun when it moves back after firing.

    V= m*v/M = 0.4*960/36 = 10.677 m/s

    Notes:
    V: the moving back velocity of gun's barrel.
    v: the projectile's muzzle velocity (960 m/s)
    M: the weigh of gun's barrel that moves back when firing (36 kg)
    m: the weight of projectile (0.4 kg).
    (Assumption that friction is 0 and just only the gun's barrel moves back after firing. In reality, the barrel when moving back will push some parts to power the gun's mechanism)

    The force needed to stop the gun's barrel moving back:

    F = 1/2*M*V*V/S = 1/2*36*10.67*10.67/0.33 = 6,210 N = 6.2 KN

    Notes:
    F: Force need to stop the gun's barrel.
    V: the move back velocity of gun's barrel (10.67 m/s)
    M: the weigh of gun's barrel that moves back when firing (36 kg).
    S: The move back distance of the gun's barrel (0.33 m).

    This calculation has proved the recoil 6 KN of 2A72 gun that mentioned by Weaponsystem.net is accuracy.

    Using the same formula to calculate the force needed to stop the 2A42 gun's barrel moving back:
    - The barrel's weight is 38.5 kg.
    - The distance moving back is 30 to 35 mm.
    The result (without muzzle brake factor) is around 62 KN.
    avatar
    The-thing-next-door

    Posts : 313
    Points : 343
    Join date : 2017-09-18
    Location : Soviet Interdimentional Command

    Re: Future of Russian IFV/BMPT

    Post  The-thing-next-door on Tue Jan 30, 2018 11:45 am

    I personally think the AGS 57 is a waste of time and they should just use the Vasilek instead

    The Vasilek has powerful HE rounds that could demolish most structures in a few hits and it also has the ability to be used is indirect fire when needed.

    It can also fire AP rounds and HEAT rounds could be made for it to give it effectiveness against enemy IFVs.


    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Tue Jan 30, 2018 10:21 pm

    kopyo-21 wrote:Just looked back the Newton formula to calculate how much force needed to stop the barrel of 2A72 gun when it moves back after firing.

    Firstly, your calculations contradict what you said earlier. Earlier, you said that 60 kN is the recoil force of the gun. 60 kN gets reduced to 6 kN by the long recoil action of the 2A72, 60 kN gets reduced to 30-40 kN by the muzzle brake of the 2A42, and 60 kN gets increased to 62 kN by the off-axis barrels in the 2A38. Why is there no 60 kN anywhere in your calculations? In your first line of calculation that the recoil force is already more than 60 kN.


    V= m*v/M = 0.4*960/36 = 10.677 m/s


    a=v^2/2m
    a=190,728 m/s^2

    Where:
    v: the projectile's muzzle velocity (960 m/s)
    m: the weight of projectile (0.4 kg).

    F=ma

    F=0.4*190,728 m/s^2 = 76.3 kN

    Secondly, your math is technically correct in the simplest of terms, but you ignored too many factors for your calculations to be comparable to the real thing. The first clue is that 60 kN is nowhere present in your calculations, neither at the beginning of the shot or when the recoiling parts are stopped. The Russian MoD and Tulamash are not spreading fake news in their technical documents and websites.


    1. The reality is that the barrel is stopped at a distance of 330-335mm, but it moves back under the small resistance of the weak return spring of the bolt for a distance of 270mm, and is stopped at 60-65mm by the strong shock absorber spring wrapped around the base of the barrel. The majority of the load is on the shock absorber, and it is the shock absorber spring that pushes the barrel back into battery, not the return spring which is just there to return the bolt back into battery. This is clearly mentioned in the technical description of the 2A72.

    2. Furthermore, you failed to account for the thrust from the propellant gasses that contribute a huge amount to the recoil force, which cannot be calculated by the momentum of the bullet/shell alone. The propellant charge in a 30x165mm cartridge weighs 0.12 kg. The exact peak velocity of those escaping gasses at the muzzle depends on the case volume, barrel length, pressure at the muzzle, density of the propellant, atmospheric pressure, and so on, but generally speaking, the velocity is 1.5 times that of the bullet or cannon shell according to the Textbook of Small Arms. In that case, the velocity is 1920 m/s. The gasses don't all come out at this velocity due to the pressure curve, so it's not possible to accurately calculate the recoil force from the momentum of the gasses as easily as bullets and cannon shells, but it is very high indeed. If you get momentum from the mass of the propellant (0.12 kg) and its peak velocity (1920 m/s), you will find that it is 2/3 the amount of the shell (230 kg.m/s vs 384 kg.m/s), but in real life it's a bit lower because of the pressure curve mentioned earlier.


    Consider these two factors in your calculations and your answer will definitely be much closer to 60 kN than 6 kN. Of course, there are more variables and nuances in the design of the cannon, so don't expect to get a very accurate answer.

    Your calculations for the 2A42 are invalid because the momentum doesn't all go into the recoiling barrel. You forgot that there is a bolt assembly with a recoil spring that works using the energy of the propellant gasses (calculate with pressure in this case, not momentum), and the recoil force from the bolt decelerating inside the cannon receiver was ignored. It may not be obvious, but the combination of recoil reduction techniques used for the 2A42 are much more effective than you think. It combines a recoiling barrel with a large muzzle brake plus a reciprocating action, which is used on some large caliber sniper rifles because of its excellent recoil reduction characteristics. See the Barrett M82 as an example. It's got a large double-baffle muzzle brake (reduces felt recoil by 70% according to Sniper: A History of the US Marksman) like the 2A42, a barrel that recoils back (by 1 inch) with each shot like the 2A42 and a reciprocating bolt that further softens the felt recoil like the 2A42.



    If you believe that the recoil force of the 2A42, 2A72 and 2A38 are 40-50 kN, 60 kN and 62 kN respectively and the recoil force of 30x165mm from a static barrel is much higher than 60 kN, then it all makes sense. For example, the recoil force from a McMillan TAC-50 with no muzzle brake is 33 kN, and that's a .50 caliber round. That's slightly more than half of the 60 kN for a 30mm round that you claimed, and 62 kN without muzzle brake as you calculated just now. Also, the recoil force from the M242 25mm cannon is 40 kN. So a 25mm cannon has only 20% more recoil force than a .50 caliber rifle and a 30mm cannon has only 2x as much recoil force? That's absurd, but that's exactly what it means if we follow your logic.

    Consider this. These numbers show the felt recoil from these guns:
    2A42: 40-50 kN
    2A72: 60 kN
    2A38: 62 kN
    M242: 40 kN
    TAC-50: 2.3 kN

    Calculated recoil force from bullet alone fired from fixed barrel, no muzzle brake:
    12.7x99mm (from 0.686 m barrel): 19.8 kN

    33/19.8=1.67
    So the recoil force from the propellant in a TAC-50 increases the recoil force by 1.67 times compared to just the recoil force from the bullet only. Apply the same multiplier to the 30 and 25mm rounds and you get 127 kN and 89.5 kN. Not the most scientific way to do things, but we lack the information to be more precise.

    So the recoil of a .50 caliber round is 33 kN, and the recoil of a 30mm round is around 120 kN. The felt recoil of the TAC-50 is only 2.3 kN despite a .50 caliber round having 33 kN of recoil force is due to a huge and quite advanced quadruple-baffle muzzle brake combined with a special hydraulic recoil dampener, and the felt recoil of the 30mm round is reduced from around 120 kN to between 40-62 kN depending on the gun that fires it. This makes a lot more sense than what you are proposing, not to mention that it corresponds to real facts from other examples.

    PS: Why does the 2A42 have almost as little recoil as an M242 even though both have muzzle brakes? Because the barrel of the 2A42 recoils by 30-35mm and there is a bolt assembly with a recoil spring inside the cannon, whereas the M242 has a fixed barrel and no reciprocating parts since it's an electrically powered chain gun. All it has is a muzzle brake. More recoil, but more accurate. This is contrary to what you said about "low recoil force = higher accuracy" because there are much more important factors to accuracy than recoil force.

    Why does the 2A38 have only a little more recoil than a long recoil cannon like the 2A72? 2A38 is a two barrel gun that works on the Gast principle, meaning that the recoil from one barrel operates the action of the other barrel. In this case, the gasses from the first barrel pushes first bolt assembly backwards and compresses the recoil spring, and the first bolt assembly pushes the second bolt assembly forward using a rack and pinion system. This means that the recoil from one shot is being absorbed by two large recoil springs: one is being compressed, and one is being extended. Also, the mass of the two bolts go in opposite directions, so a part of the recoil forces are cancelled out (like in the Russian counter-recoil rifles). This adequately explains why the recoil force is halved compared to the calculated 127 kN.

    Hopefully that explains everything for you.
    avatar
    Isos

    Posts : 1215
    Points : 1213
    Join date : 2015-11-06

    Re: Future of Russian IFV/BMPT

    Post  Isos on Wed Jan 31, 2018 12:25 am

    What do you guys think of a new high velocity 76 or 100 mm gun for a new hybrid ligh tank based on t-15 without the space for soldier but with more protection ?

    There are more and more better armoured IFV in countries around Russia so it could act like a light vehicle/IFV chaser. Tanks are not the most used vehicle in the west, they often rely on less armoured but more mobile vehicles.

    None of them could survive a 76 or 100 sabot or HEAT round and it could even damage badly MBTs from behind or from the sides. They will have more rounds to fire than the actual number of missiles they carry so more targets destroyed per vehicles.

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Wed Jan 31, 2018 2:00 am

    Finally you only have a float left to hold, that is the numbers from Tula's site. However, when the numbers (recoil forces) can not explain the contradictive reality, I have reasons to double they have purposely twisted the numbers or mixed oranges with apples in the same box to fool poor readers.

    For 2A42 and 2A72 guns, the reality of using 2A72 to upgrade old vehicles that could only installed 14.5mm gun before and to equip newly produced light and super-light combat vehicles has shown who is wrong, who is right about recoil of 2A72 gun  vs. 2A42 gun.

    And the "superior" (accoding to many military experts) BMPTs "project 781" used double 2A72 gun unstead of 2A42 gun like the "inferior/looser" (also accoding to many military experts) Terminator-2.

    Another very clear example that no one can not deny is the 125mm 2A75 gun of Sprut-SD light tank. It uses the long-recoil (700 mm) to reduce the significant recoil force compare to the 2A46M gun (recoil 300 mm) of heavy T-72/80/90 tanks.

    About 2A38 gun, you are totally wrong. It use completely gas-operation, gas from this barrel when firing will push the piston, powering the loafing mechanism of the other barrel. The pistons when moving back will help to reduce the recoil force (as Newton formula I mentioned in previous post).

    Conclusion:

    Aaccording to Newton formula about reservation of momentum, the gun recoil will depend on:

    - The weight and muzzle velocity of projectile.
    - The weight of gun's parts that move back when firing (barrel, etc)
    - The distance of moving back.

    This explain clearly the reasons why the recoil of 2A72 gun is just ~ 1/10 of 2A42 gun:

    - The weight and muzzle velocity of projectile is the same (04 kg and 960 m/s).
    - Its moving distance is 10 times higher than 2A42 gun's (330 mm vs 30-35 mm).
    - The weigh of gun's moving parts (barrel, bolt, etc) supposed to be quite the same with 2A42 gun's (36++ kg vs 38.5 kg).
    avatar
    GarryB

    Posts : 17213
    Points : 17819
    Join date : 2010-03-30
    Location : New Zealand

    Re: Future of Russian IFV/BMPT

    Post  GarryB on Wed Jan 31, 2018 4:03 am

    What do you guys think of a new high velocity 76 or 100 mm gun for a new hybrid ligh tank based on t-15 without the space for soldier but with more protection ?

    You need to look at targets on the battlefield and see what is needed to deal with problems... one example is the early multi turreted tanks that had a low velocity 76.2mm gun for HE power and small calibre 37mm or 45mm cannon to penetrate the thin armour of the time.

    The standard T-34 had a medium pressure 76.2mm gun instead of a high velocity 57mm gun... at the time the Germans introduced an anti tank 50mm gun and a low velocity 76.2mm gun for their tanks.

    Why not go for a high velocity 76.2mm gun?

    High velocity guns have large shell casings and are heavy and bulky and generate lots of recoil on firing.

    If a smaller lighter gun will do the job why go bigger and heavier and more expensive than you need to.

    Why not develop 203mm guns for infantry vehicles and tanks... low velocity for IFVs and high velocity for tanks?

    the simple fact is that the 125mm gun is fine for "light" tanks... and anything armata based is not a light anything.

    The main problem with airburst ammo is its general cost... to get effective airbursts the traditional method is a very very precise time keeping component inside the projectile... that is generally rather expensive... but without extreme accuracy it will not explode where you want it to... making it rather useless... detonating directly over a trench is effective... 5m past or before the trench and it is useless.

    Using a laser beam to tell it when to explode means the expensive precise time keeping bits can be in the vehicle and completely reuseable... making the ammo much much cheaper... and if you want to use it a lot then cheap ammo is critical.

    Air burst 40mm grenades and 57mm grenades will be incredibly potent rounds on the battlefield because they both have the round capacity for a decent amount of HE and fragments and a fuse to set it off at the right time.

    The South Africans were impressed with the 30mm cannon of the BMP-2 too... it is a very good weapon... and with new ammo types that are cheap enough to actually use it will become even better...


    Another very clear example that no one can not deny is the 125mm 2A75 gun of Sprut-SD light tank. It uses the long-recoil (700 mm) to reduce the significant recoil force compare to the 2A46M gun (recoil 300 mm) of heavy T-72/80/90 tanks.

    It does not make the gun in the Sprut more accurate... it just means it can be used in a much lighter vehicle.

    The long recoil method does not reduce recoil... it reduces felt recoil by spreading it over time.


    _________________
    “The West won the world not by the superiority of its ideas or values or religion […] but rather by its superiority in applying organized violence. Westerners often forget this fact; non-Westerners never do.”

    ― Samuel P. Huntington, The Clash of Civilizations and the Remaking of World Order

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Wed Jan 31, 2018 4:54 am

    That is just how we explain about long recoil. The longer the moving back is, the less stronger the recoil is. Therefore, the correct should be "it reduces felt recoil by spreading it over the moving back".
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Wed Jan 31, 2018 5:09 am

    kopyo-21 wrote:Finally you only have a float left to hold, that is the numbers from Tula's site. However, when the numbers (recoil forces) can not explain the contradictive reality, I have reasons to double they have purposely twisted the numbers or mixed oranges with apples in the same box to fool poor readers.

    And the authors of the technical manual for the 2A72 wanted to deceive the poor soldiers as well? Good theory.

    BTW I love how you basically just ignored everything I said. So according to you, a 2A42 only has a little more recoil than a .50 caliber sniper rifle without a muzzle brake (30-40 kN vs 33 kN) Laughing


    For 2A42 and 2A72 guns, the reality of using 2A72 to upgrade old vehicles that could only installed 14.5mm gun before and to equip newly produced light and super-light combat vehicles has shown who is wrong, who is right about recoil of 2A72 gun  vs. 2A42 gun.

    Yeah. Right.



    Amazingly, Muromteplovoz engineers have achieved an impossible task long ago. Bravo!



    Watch a BTR-80 with a 2A42 fire:



    Even a BTR-60 can have a 2A42:



    An OT-64 SKOT can have a 2A42 as well. Its technical characteristics are the same as the BTR series, and weighs 13 tons like the BTR-80.




    The 2A72 cannon, due to the use of a moving barrel scheme, transfers to the roof of the armored object a more extended recoil momentum, which means it has a smaller maximum recoil force, which makes it possible to use it on light armored vehicles such as BTR-82, Tigr- M with armored corps made of sheets with a thickness of only about 7mm, on which the use of armament more powerful than the 14.5 mm KPVT machine gun before the appearance of the 30mm gun 2A72 was previously impossible

    This is so obviously wrong that it's hilarious. The roof of the BMP-1 is 6mm thick, and the roof of the BMP-2 is also 6mm thick, and yet, both can have a 2A42 installed. Take the Turra 30 turret, for example. And what about that BMP-1-30 with a BMD-2 turret?



    Don't forget that the BMD-2 itself is incredibly light. It is 8.22 tons combat loaded with full ammo, full fuel, oil, etc. Uran-9 weighs 10 tons. Please, try to tell everyone that BMD-2 is not a "super light combat vehicle". Moving on: The roof of the PT-76 is 6mm thick. They can install a 2A42 on it too.



    What about a BTR-50P? No problem.



    Oh, and look, an MT-LBu firing a 2A42! As we all know, MT-LBu is a heavy combat vehicle Laughing BTW, those shot groupings are really nice. Another case of "more recoil force=less accuracy", I'm sure you will agree...  Laughing



    Another one, this time a BPM-97:



    BPM-97 weighs 10 tons. ~3 tons less than a BTR-80, and the same weight as an Uran-9. What is your criteria for "super light" anyway?  Laughing

    2A42 installed in K-4386 Typhoon-VDV, which weighs 13.5 tons - same as BTR-80. Looks like Russian engineers are defying your words each day.



    Nimr MECV, a humvee sized patrol vehicle:



    AMX-13 APC:



    There are more offerings by various manufacturers. CM30 one-man turret with 2A42 for BTR-60/70/80, DVK-30 for the BTR-70/80, and Burevestnik's 30mm RCWS designed for Typhoon.

    Heck, even a 2.5 ton AU-220M turret with a 57mm gun can be installed on a BTR-80. The nonsense about the 2A72 being some kind of wonder weapon that can transform an APC with 14.5mm machine gun into an IFV with a 30mm cannon because of its miraculous long recoil system (that can give 30mm cannon less recoil force than KPVT, apparently) is just that - nonsense, rubbish advertising, horseshit marketing lies, bullshit falsehoods, and so on. I think you understand. At least, I hope that you understand.



    Please stop saying things that are obviously wrong, and you won't be wrong. It's very simple Sad


    And the "superior" (accoding to many military experts) BMPTs "project 781" used double 2A72 gun unstead of 2A42 gun like the "inferior/looser" (also accoding to many military experts) Terminator-2.

    "Better" in what way? 781 had two independently traversing turrets. That is probably better than one turret. The chassis and hull was also different from what we see today. Was that better? Who knows? I'm pretty sure you don't know either, unless you have some juicy insider information to tell us. Unless the 2A72 was specifically mentioned to be better than the 2A42, you are basically making a huge leap of faith with that assumption.


    Another very clear example that no one can not deny is the 125mm 2A75 gun of Sprut-SD light tank. It uses the long-recoil (700 mm) to reduce the significant recoil force compare to the 2A46M gun (recoil 300 mm) of heavy T-72/80/90 tanks.

    This may be surprising to you, but all cannons use long recoil hydraulic recoil mechanisms. Increasing the recoil distance does decrease the recoil force. The only question is how long the recoil distance is for the 2A72. As I said before - and you did not listen, and you will not listen - the barrel is stopped in a distance of 60-65mm by the shock absorber. Oh, it's not true? Wow, they really love lying to their mechanics, technicians and soldiers, don't they! They really don't care if the people who have to work with and maintain these guns understand them!


    About 2A38 gun, you are totally wrong. It use completely gas-operation, gas from this barrel when firing will be used push the piston, powering the mechanism of the other barrel. The pistons when moving back will help to reduce the recoil force (as Newton formula I mentioned in previous post).

    Read what I wrote again. Or maybe you don't understand what a Gast gun is?


    Conclusion:

    Aaccording to Newton formula about reservation of momentum


    How does a muzzle brake reduce recoil force? Magic? Let me give you a hint: the gasses that comes out of a gun barrel have momentum and energy

    I apologize to everyone for this photo dump, but when someone is wrong, they are wrong. Reality does not change at a whim, and physics does not is physics whether you like it or not.

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Wed Jan 31, 2018 7:34 am

    Somethings to answer your questions:

    1. 2A72 gun's barrel moves back 330 mm after firing. The 2A42 gun's barrel moves back 30-35 mm after firing.

    2. Your owned copy "2A38 is a two barrel gun that works on the Gast principle, meaning that the recoil from one barrel operates the action of the other barrel" is still there.

    You are totally wrong. The 2A38 gun's barrel are fixed so can not use the term "recoil" here. The correct must be "2A38 is a two barrel gun that works on the Gast principle, meaning that the gas blowing back from one barrel operates the action of the other barrel".

    3. You posted a lot of photos so please show me which ones are already bought and in services now. Or they are just prototypes for showing off and no one buy finally? For example, show me how/where is the BTR-82A1 with 2A42 gun now?

    Do you need me bomb photos of light combat vehicles with 2A72 that have veen bought and in services now?

    4. Muzzle brake: Do you not understand this very simple and need me to explain it for you?
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Wed Jan 31, 2018 8:48 am

    kopyo-21 wrote:

    1. 2A72 gun's barrel moves back 330 mm after firing. The 2A42 gun's barrel moves back 30-35 mm after firing.

    If I throw a rock at a cushion that is 10 m away from me, and the rock stops in the cushion after penetrating 0.1 m, did the rock take 10.1 m to decelerate to a stop, or did it take 0.1 m to decelerate down to a stop? (Ignore air resistance) Come on, think! You can do it! I believe in you!

    BTW I really love how your story changed.

    When firing, most of 60KN recoil force will be used to power the gun system so the recoil left 6KN on the turret finally (as my source mentioned)

    In the opposite way, the 2A42 guns mainly use the gas from the cartridge power burning to operate the gun system. When firing Its recoil according to Tula's is 50-60KN. The 30-40KN as mt source mentioned should be the recoil left on the turret finally.

    So you started off saying that Tula's given number of 60 kN of 2A72 is reduced to 6 kN, and 40-50 kN of 2A42 gets reduced to 30-40 kN. Tula's data is the raw recoil force without including the muzzle brake, and weaponsystems.net's data is the final recoil force with a muzzle brake. Then you said that the muzzle brake of the 2A42 is responsible for the lower (40-50 kN vs 60 kN) recoil force compared to 2A72.

    It is very simple and no need to talk too long & too much. The 2A42 and the 2A72 fire the same rounds, have the same barrel length and barrel design so basically, according to Newton, they will produce the same recoil force. According to Tula's data, the 2A42 guns produce less recoil than 2A72. This simply because of muzzle brake on 2A42 but 2A72.

    So Tula's data already includes the muzzle brake in this new story  Very Happy At first, it was 40-50 kN gets reduced to 30-40 kN. Then 2A42 suddenly has the same recoil force as 2A72, so now it is 60 kN gets reduced to 30-40 kN.

    After you did your little calculations, you switched course and changed your stance entirely:

    Finally you only have a float left to hold, that is the numbers from Tula's site. However, when the numbers (recoil forces) can not explain the contradictive reality, I have reasons to double they have purposely twisted the numbers or mixed oranges with apples in the same box to fool poor readers.

    Now you're saying that Tula is giving false numbers.

    Conclusion: You are a clown. Your argument is inconsistent, self-contradictory, and inconsistent with real data. You are making this up as you go along  Wink


    kopyo-21 wrote:
    2. Your owned copy "2A38 is a two barrel gun that works on the Gast principle, meaning that the recoil from one barrel operates the action of the other barrel" is still there.

    You are totally wrong. The 2A38 gun's barrel are fixed so can not use the term "recoil" here. The correct must be "2A38 is a two barrel gun that works on the Gast principle, meaning that the gas blowing back from one barrel operates the action of the other barrel".

    Now I know why you ignore huge chunks of my posts. You are blind!

    You must read this part that I wrote about the 2A38:

    In this case, the gasses from the first barrel pushes first bolt assembly backwards and compresses the recoil spring, and the first bolt assembly pushes the second bolt assembly forward using a rack and pinion system.

    Like in all the other cases, you only saw what you wanted to see. Yes, I did write "recoil", and then I followed up with an explanation about what it meant in the case of the 2A38. You really have to stop trying to bend reality. It doesn't work.

    kopyo-21 wrote:
    3. You posted a lot of photos so please show me which ones are already bought and in services now. Or they are just prototypes for showing off and no one buy finally? For example, show me how/where is the BTR-82A1 with 2A42 gun now?

    Do you need me bomb photos of light combat vehicles with 2A72 that have veen bought and in services now?

    You were just shown that it was in fact possible to mount 2A42 on the BTR-80 and other light vehicles, and you were shown that a BTR-80 with a 2A42 was able to fire on the move when you said that it was not possible, and now you are trying to change the topic because you were proven to be completely wrong:

    If they want to keep the firing accuracy while on stop and while on move, they will have to reinforce gun mounting, turret, hull and chassis. In that case, the vehicles will gain a significant weight that may ask for changing engine, reducing the protection level, etc.

    Of course, no such thing was required. You saw the video of a BTR-80 with a 2A42 firing on the move. The turrets offered by Muromteplovoz and other companies are drop-in turrets that require no prior modification to the vehicle. Whether these turrets are widespread is another matter entirely. If, according to you, large recoil forces from 2A42 reduces its accuracy because it's mounted on such light vehicles, it still won't be as bad as a 2A72 that was mounted on a BTR-80A and BTR-82A without a barrel support, which goes against all logic. You yourself gave a quote that said the same thing:

    The fee for using the scheme with a movable barrel was a somewhat worse accuracy

    So why did they mass-produce the 2A72 for the BTR-82A without a barrel support when the 2A72 on the Uran-9 and Tigr-M have barrel supports? Accuracy definitely wasn't a priority, it appears. As to whether or not these 2A42 turrets are used at all: best example is the BMD-2. It is very common, and it is the lightest vehicle among all of the light vehicles you mentioned, including the Uran-9. Also, Typhoon-VDV is lighter than the BTR-82A, and it's a 4x4 so it's a light combat vehicle by any reasonable criteria. Some other turrets like the DVK-30 have not yet received any contracts, but it's most likely because it has an externally mounted Fagot/Konkurs missile launcher, and the gunner has to come out of his hatch to use it. That would be a dealbreaker, of course. There are many factors that go into such things, but the important thing is that it is in fact more than possible to install a 2A42 on light vehicles with a roof of 7mm or even 6mm. Once you acknowledge this fact, you can move on with your life.

    kopyo-21 wrote:
    4. Muzzle brake: Do you not understand this very simple and need me to explain it for you?

    No, you must explain it to me, unfortunately. So according to you:

    30x165mm (fixed barrel, no muzzle brake): 60 kN
    12.7x99mm (fixed barrel, no muzzle brake): 33 kN

    You see, a muzzle brake can reduce the recoil of a rifle or a cannon by 70-80% according to The Basics of Artillery Guns and Ammunition by A.Y Derevyanchuk. Why you think that the Russians are so stupid that a muzzle brake + a recoiling barrel can only reduce the recoil force of a 2A42 from 40-50 kN to 30-40 kN or even 60-62 kN to 30-40 kN is a mystery to me, because that is only a 20-25% reduction in recoil force, ~50% at the max if we assume that your earlier calculations for 2A42=62kN are correct. Also, you know what a muzzle brake is, so you must know that it uses the energy and momentum from the propellant gasses to push the rifle/cannon forward to reduce rearward recoil, yes? So you realize that propellant gasses have energy and momentum. Then why do you ignore it?

    Anyway, that's not the point: 33 kN from a TAC-50 is only reduced to 6.6 kN by a high efficiency muzzle brake (80% reduction in recoil force) at the most. McMillan offers an R2 hydraulic recoil mitigation system that reduces this further to 2.3 kN, but regular TAC-50 rifles do not have the R2 hydraulic recoil mitigation system, just a muzzle brake. So basically, if you had a regular TAC-50 with only a muzzle brake, it would produce 6.6 kN of recoil force and people can fire it on their shoulders without any injury or even discomfort. That means that the 2A72 with 6 kN of recoil force can be fired from the shoulder or from a bipod as well.

    According to your logic:
    2A72: 6 kN
    TAC-50: 6.6 kN

    I wish I could go to your house, so that you can look me in the eye with a straight face and say it out loud: "Recoil force of 2A72 is less than .50 caliber sniper rifle with muzzle brake". Laughing Laughing Laughing Laughing Laughing Laughing Laughing Laughing I swear, you should either be on a stage or in a mental hospital.
    avatar
    George1

    Posts : 11069
    Points : 11546
    Join date : 2011-12-22
    Location : Greece

    Re: Future of Russian IFV/BMPT

    Post  George1 on Wed Jan 31, 2018 1:27 pm

    Russian machine builder vows to fulfill deliveries of Terminator AFVs by early 2019

    The Russian Defense Ministry signed a contract to deliver Terminators during the Army-2017 forum

    MOSCOW, January 31. /TASS/. The implementation of the contract to deliver Terminator tank support armored fighting vehicles will be completed in early 2019, and the army will get the first batch in March -April 2018, the Research and Production Corporation Uralvagonzavod told TASS.

    "It [the contract - TASS] is long-term. We plan to deliver the first batch of the tank support fighting vehicles this March - April. The whole contract will be completed by early 2019. The volume of deliveries is confidential, but overall it provides for the organization of operational testing for these specified products," the corporation said.

    Chief of the Main Armored Directorate of the Russian Defense Ministry Lieutenant General Alexander Shevchenko earlier said that the Terminator AFV would become operational in 2017. He noted that "this is a brand-new class of vehicle" "that many countries, chiefly Israel and Syria, are interested in." The general specified that the AFV had successfully passed all test operations.

    The Russian Defense Ministry signed a contract to deliver Terminators during the Army-2017 forum. The agreements that the defense ministry and Uralvagonzavod inked then are worth over 24 bln rubles ($426.3 mln) The Terminator has a 44-tonne combat weight, according to the producer’s website. The vehicle is outfitted with two 30-mm-caliber 2A42 automatic guns and 7.62-mm-caliber PKT coaxial tank machine gun.


    More:
    http://tass.com/defense/987812


    _________________
    "There's no smoke without fire.", Georgy Zhukov


    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Thu Feb 01, 2018 1:33 am

    @ Interlinked

    Posts after posts, they become not only my logic and the reality but also the calculations that follows the Newton's momentum conservation. You write a lot, provide a lot of your assumption to avoid facing with both physics laws and reality:

    1. Physics laws:  According to the Newton's momentum conservation law, both 2 guns 2a42 and 2a72 fire same bullet (0.4 kg) with the same muzzle velocity (960 m/s) so right after the bullet leaving the barrel, both 2 guns must whistand the same momentum back (initial recoil).

    Besides that, also right after the bullet leaving the barrel, the burning gas throut out from the gun muzzel makes gun like a rocket and the second recoil appears. Both 2 guns fire the same rounds (the same cartridge powder), have the same barrel length and groves design so their secondary recoil are the same.

    However, the  2A42 gun use the muzzle brake that helps to reduce the secondary recoil therefore its total recoil is lower than 2A72 at the moment the bullet leaving the barrel. (Don't make your owned assumption about the muzzle brake of 2A42 gun reduces 90% of recoil force)

    I wrote so long like that to explain you and prove why I said both 2 guns produce the same recoil when firing but the muzzle brake makes the total recoil of 2A42 lower than 2A72

    Also according to the Newton's momentum conservation law, right after receiving the recoil, both 2 gun's barrels move back to balance the force. It reduces the recoil by spreading it over the moving back so the longer moving back is, the lower force needed to stop is.

    The 2A72 gun's barrel moves back 330 mm, much more (around 10 times) higher than the 30-35 mm of 2A42 gun's barrel so it spreads out the recoil much more effectively (around 10 times as calculation) than 2A42 gun. Therefore when the barrels stop (after 330 mm in 2A72 and after 30-35 mm in 2A42), the force that 2A72 gun's barrel push on the gun is much less than 2A42 gun's barrel do.

    "To reduce the impact of the gun's release, the barrel is absorbed and recedes 30 to 35 mm when firing."
    http://www.arms-expo.ru/armament/samples/1300/59779/

    Comparison with the 2A42 gun: The 2A72 cannon, due to the use of a moving barrel scheme, transfers to the roof of the armored object a more extended recoil momentum, which means it has a smaller maximum recoil force, which makes it possible to use it on light armored vehicles such as BTR-82, Tigr- M with armored corps made of sheets with a thickness of only about 7 mm, on which the use of armament more powerful than the 14.5 mm KPVT machine gun before the appearance of the 30mm gun 2A72 was previously impossible..
    http://www.history147.ru/2017/09/blog-post.html?m=1

    "The 2A72 cannon, due to the application of the scheme with a movable barrel, transfers a more extended recoil momentum to the roof of the armored object, as compared to the gas escape line on 2A42, and therefore has a smaller maximum value of the instantaneous recoil force (7 tons versus 20 tons for 2A42 with fixed barrel)"
    https://ru.m.wikipedia.org/wiki/30-мм_пушка_2А72

    "The 2A72 cannon, due to the application of the scheme with a movable barrel, transfers a more extended recoil momentum to the roof of the armored object, as compared to the gas escape line on 2A42, and therefore has a smaller maximum value of the instantaneous recoil force (7 tons versus 20 tons for 2A42 with fixed barrel), which allows use it on light armored vehicles such as BTR-82, Tigr-M with armored corps made of sheets with a thickness of only about 7 mm, on which the use of armament more powerful than the 14.5 mm KPVT machine gun before the appearance of 30mm gun 2A72 was previously impossible."
    https://wikivisually.com/lang-ru/wiki/2А72

    PS: I give all of suorces above not for the "7 tons" and the "20 tons" numberd as I can not determine where are come from. Just want to re-confirm that the 2A72, thank to its longer-recoil operation, has push much lower force on the turret and whole vehicles than the 2A42 do.

    2. The reality: Sofar, all projects that upgrade or newly produce wheeled combat vehicles that have been bought by both domestic and oversea like BTR-80A, BTR-82A, BTR-3/4 in Russia and Ukraine have been using 2A72 instead of 2A42. In contrasts, no one has bought vehicles with 2A42 gun like BTR-90, BTR-82A1, etc.

    PS 1: BTW, you should revise the data about firing accuracy of 2A42 in your blog. The given data is totally incorrect that may makes you and your readers percept wrongly not only about 2A42 bust also about 2A72.

    PS 2: The 2A42 is nothing better than the 2A72 (with barrel's rigid sleeve support) but only ROF.

    PS 3: In the contrasts, the 2A42 is bigger, more expensive, smockier and much more recoil than the 2A72.

    PS 4: Sofar, you still can not prove anything that you use to fight back my points, suggest replacing the 2A42 by 2A72 on new generation of BMPT.
    avatar
    GarryB

    Posts : 17213
    Points : 17819
    Join date : 2010-03-30
    Location : New Zealand

    Re: Future of Russian IFV/BMPT

    Post  GarryB on Thu Feb 01, 2018 6:11 am

    The primary purpose of the 2A72 was to eliminate the problem of fumes in the turret of the BMP-2.

    As fumes are not an issue for helicopter mounts or the new generation of armoured vehicles which have unmanned turrets I fail to see the advantages of the 2A72... especially now at a time where most of its applications are being replaced by larger calibre weapons.


    _________________
    “The West won the world not by the superiority of its ideas or values or religion […] but rather by its superiority in applying organized violence. Westerners often forget this fact; non-Westerners never do.”

    ― Samuel P. Huntington, The Clash of Civilizations and the Remaking of World Order

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Thu Feb 01, 2018 6:28 am

    Just read an artical on BTVT that reconfirms that, each gun of 2A42 on BMPT-72 is feeded 1 type of rounds, either HEI or API, and fired in turn instead of mixed rounds and fired simultaneously.

    Both 2 2A42 gun are hang either off-right or off-left of turret axis so when only 1 gun fires, it will tend to spin the turret due to its very strong recoil. In that case, the firing accuracy is a big question.

    http://btvt.info/1inservice/tom3_bmpt_weapon.htm

    PS: The BMPT project 781, that was much highly evaluated by many military experts than the current BMPT-72, chose using double 2A72 gun instead 2A42 gun.



    Last edited by kopyo-21 on Thu Feb 01, 2018 6:51 am; edited 1 time in total

    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Thu Feb 01, 2018 6:37 am

    GarryB wrote:The primary purpose of the 2A72 was to eliminate the problem of fumes in the turret of the BMP-2.

    As fumes are not an issue for helicopter mounts or the new generation of armoured vehicles which have unmanned turrets I fail to see the advantages of the 2A72... especially now at a time where most of its applications are being replaced by larger calibre weapons.
    The smocky issue may be the primary reason they created the 2A72. However, if we think about the 2A72 gun is installed off-right of BMP-3's turret axis, the recoil may be also the primary reason.

    Nowaday, it has shown the "less smock" is just one of some 2A72 gun's advantages that help it more suitable for light/small combat vehicles.

    - Much less recoil.
    - Smaller.
    - Cheaper.

    Don't forget that the 2A72 was created after the 2A42 and by the same team so I have reason to believe that it was designed with issues of 2A42 in mind.
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Thu Feb 01, 2018 8:32 pm

    kopyo-21 wrote:
    Posts after posts, they become not only my logic and the reality but also the calculations that follows the Newton's momentum conservation. You write a lot, provide a lot of your assumption to avoid facing with both physics laws and reality:

    Laughing

    kopyo-21 wrote:
    1. Physics laws:  According to the Newton's momentum conservation law, both 2 guns 2a42 and 2a72 fire same bullet (0.4 kg) with the same muzzle velocity (960 m/s) so right after the bullet leaving the barrel, both 2 guns must whistand the same momentum back (initial recoil).

    Besides that, also right after the bullet leaving the barrel, the burning gas throut out from the gun muzzel makes gun like a rocket and the second recoil appears. Both 2 guns fire the same rounds (the same cartridge powder), have the same barrel length and groves design so their secondary recoil are the same.

    You acknowledge the rocket effect of propellant gasses, and then you don't care about it. In your calculations, you used the momentum of the 0.4 kg projectile, and then ignored the propellant gasses entirely... You like to talk about "law of Newton" and "physics laws" when it suits you, and then you ignore them when they are inconvenient. You do this because you know that when you add the propellant gasses into the equation, the recoil force jumps from 6.2 kN to something much, much higher... and your illusion is shattered. So of course, you prefer to pretend that it does not exist  Wink

    kopyo-21 wrote:
    However, the  2A42 gun use the muzzle brake that helps to reduce the secondary recoil therefore its total recoil is lower than 2A72 at the moment the bullet leaving the barrel. (Don't make your owned assumption about the muzzle brake of 2A42 gun reduces 90% of recoil force)

    I wrote so long like that to explain you and prove why I said both 2 guns produce the same recoil when firing but the muzzle brake makes the total recoil of 2A42 lower than 2A72

    Also according to the Newton's momentum conservation law, right after receiving the recoil, both 2 gun's barrels move back to balance the force. It reduces the recoil by spreading it over the moving back so the longer moving back is, the lower force needed to stop is.

    The 2A72 gun's barrel moves back 330 mm, much more (around 10 times) higher than the 30-35 mm of 2A42 gun's barrel so it spreads out the recoil much more effectively (around 10 times as calculation) than 2A42 gun. Therefore when the barrels stop (after 330 mm in 2A72 and after 30-35 mm in 2A42), the force that 2A72 gun's barrel push on the gun is much less than 2A42 gun's barrel do.

    "To reduce the impact of the gun's release, the barrel is absorbed and recedes 30 to 35 mm when firing."
    http://www.arms-expo.ru/armament/samples/1300/59779/

    Just because the barrel moves back by 330-335mm does not mean that it decelerates at the same rate throughout. Here's what the technical description (Техническое описание и инструкция по эксплуатации 30-мм автоматической пушки 2А72.00.000.TO) for the 2A72 says:

    При выстреле ствол вместе с затвором под действием пороховых газов на дно гильзы движется назад.

    Ствол с затвором первоначально движется назад свободно сжимая возвратную пружину.

    Пройдя=270мм начинают сжимать пружину аммортизатора. Сжав ее на 60-65мм энергия отката ствола поглощается, и они останавливаются.


    Translation:

    When a shot is fired, the barrel, together with the bolt, moves backward under the action of the powder gases on the bottom of the cartridge case.

    The barrel with the bolt initially moves backwards freely compressing the return spring.

    Passing=270mm begins to compress the spring of the shock absorber. Compressing it by 60-65mm, the energy of the moving barrel is absorbed, and they stop.


    You tell me, what does it say about how far the barrel needs to stop? Keep in mind that the return spring is a tiny little spring whereas the shock absorber spring is a massive coil spring that wraps around the barrel, as you can see below (2. shock absorber, 6. return spring):



    Deceleration is low when the return force is low, and deceleration is high when the return force is high. When the barrel is only compressing the tiny return spring, the barrel only loses a few meters/second in a long span of time, but when it compresses the huge shock absorber spring, it decelerates very quickly within a distance of 60-65mm. The small return spring is much smaller than the return spring for the 2A42, which has a much larger bolt carrier and bolt than the 2A72 so it needs a bigger return spring. Also, the bolt is unlocked from the barrel very early in the recoil stroke, so the barrel isn't pushing against the return spring for the majority of the 270mm it travels before it contacts the shock absorber spring. That is why the technical description says "moves backwards freely". The barrel is barely slowing down at all before it contacts the shock absorber.

    kopyo-21 wrote:
    http://www.history147.ru/2017/09/blog-post.html?m=1

    https://ru.m.wikipedia.org/wiki/30-мм_пушка_2А72

    https://wikivisually.com/lang-ru/wiki/2А72

    PS: I give all of suorces above not for the "7 tons" and the "20 tons" numberd as I can not determine where are come from. Just want to re-confirm that the 2A72, thank to its longer-recoil operation, has push much lower force on the turret and whole vehicles than the 2A42 do.

    All these websites basically copy from ru.wikipedia, and the relevant paragraph from ru.ikipedia.ru has 0 sources. Literally 0. The page that you are quoting from was first edited by an anonymous user on the 22rd of April 2017, who added the stuff about the 7mm roof: https://ru.wikipedia.org/w/index.php?title=30-%D0%BC%D0%BC_%D0%BF%D1%83%D1%88%D0%BA%D0%B0_2%D0%9072&direction=next&oldid=85004226

    The second edit was made on June 29 and made a minor grammatical change, but it was otherwise identical. The third edit was done by another anonymous user on the 5th of September 2017, who added the "7 tons vs 20 tons" statement without listing sources. If you compare this version of the wiki article with the previous versions, there were no changes in the references list: https://ru.wikipedia.org/w/index.php?title=30-%D0%BC%D0%BC_%D0%BF%D1%83%D1%88%D0%BA%D0%B0_2%D0%9072&direction=next&oldid=86258286

    You were unable to find a source for "7 tons" and "20 tons" of recoil because those numbers were completely made up. 7 tons of recoil force is equal to 68 kN, and 20 tons is equal to 196 kN, which is absurd, of course. Just another case of article vandalism. It's pretty obvious that Wikivisually is just a website that automatically copies content from Wikipedia but with a photo gallery on the right side of the page, if you bothered to read the top right corner of the page you quoted, and the history147.ru blog article is also directly copied from Wikipedia. Compare them:

    history147 blog:
    Пушка 2А72 за счет применения схемы с подвижным стволом, по сравнению с газоотводной на 2А42 передает на крышу бронеобъекта более растянутый по времени импульс отдачи, а значит имеет меньшее максимальное значение силы отдачи, что позволяет использовать ее на легкой бронетехнике типа БТР-82, Тигр-М с бронекорпусами выполненными из листов толщиной всего около 7 мм, на которой применение вооружения мощнее 14,5мм пулемета КПВТ до появления 30мм пушки 2А72 ранее было невозможно. Это ставит, по огневым возможностям, их на один уровень более тяжелыми и дорогими БМП и значительно повышает боевую ценность легких бронемашин в обороне (когда бой ведется из окопа и уровень бронезащиты боевой машины не столь важен).

    Wikipedia edit from the 29th of June, 2017:

    Пушка 2А72 за счет применения схемы с подвижным стволом, по сравнению с газоотводной на 2А42 передает на крышу бронеобъекта более растянутый по времени импульс отдачи, а значит имеет меньшее максимальное значение силы отдачи, что позволяет использовать ее на легкой бронетехнике типа БТР-82, Тигр-М с бронекорпусами выполненными из листов толщиной всего около 7 мм, на которой применение вооружения мощнее 14,5мм пулемета КПВТ до появления 30мм пушки 2А72 ранее было невозможно. Это ставит, по огневым возможностям, их на один уровень более тяжелыми и дорогими БМП и значительно повышает боевую ценность легких бронемашин в обороне (когда бой ведется из окопа и уровень бронезащиты боевой машины не столь важен).


    Would it be a surprise to you if I told you that the history147.ru article was written on the 3rd of September, 2017? Just two days before the Wikipedia article on the 2A72 was edited on the 5th of September and the "7 tons vs 20 tons" rubbish was added, and for that reason, the history147.ru article is only identical to the Wikipedia page on the 2A72 from June 29. So in summary:


    • April 22: "7mm roof" appears on Wikipedia without references or sources of any kind

    • June 29: Minor grammatical change

    • September 3: history147.ru article copies June 29 version of Wikipedia article on 2A72

    • September 5: "7 tons vs 20 tons" appears on Wikipedia without references or sources of any kind



    The "7mm roof" claim was originally made on a Wikipedia article and has no sources, and the author of that claim was an anonymous person from Moscow, so nobody with a name is taking responsibility for it. No wonder, since it's such a stupid claim! The BMP-2 has a roof that is 6mm thick, and guess what cannon it has? This little detail allows us to conclusively confirm that all of the sources you listed are in fact direct copy-and-paste jobs taken from an unsourced Wikipedia article. Your sources get worse and worse. First it was weaponsystems.net, a website with articles written by anonymous authors and has no references or sources, and now it's Wikipedia, a website with an article written by an anonymous author that has no references or sources. This is what you're leaning on. These are your sources. This is what you're basing your entire argument on.  Laughing

    kopyo-21 wrote:
    2. The reality: Sofar, all projects that upgrade or newly produce wheeled combat vehicles that have been bought by both domestic and oversea like BTR-80A, BTR-82A, BTR-3/4 in Russia and Ukraine have been using 2A72 instead of 2A42. In contrasts, no one has bought vehicles with 2A42 gun like BTR-90, BTR-82A1, etc.

    Again you talk about this. Many products have been offered over the years, not all have entered service. It's natural. Often it's about manufacturing capabilities. Muromteplovoz makes turrets with a 2A42 that could have been used for the BTR-82A, but they also had the same turret except with a 2A72 instead of a 2A42, so they could have bought that instead. See photo:



    Why not? Maybe Muromteplovoz does not have the kind of manufacturing capacity to produce thousands of turrets. After all, they have been mostly doing overhaul work for years. Speaking of the BTR-82A, you need to realize that even though the BTR-80A, BTR-82A, and BRM-3K all have a 2A72, the barrels on their guns are unsupported. What happens when the barrel is unsupported? According to a proposal document titled Новые Технологии Создания Малокалиберных
    Автоматических Пушек
    :

    Например, в одной из работ была выбрана 30-мм пушка 2А72 широко применяемая в сухопутных войсках. Достоинством этой пушки является селективное питание и надежность. Пушка имеет низкий темп стрельбы, он составляет около 400 выстр./мин., что позволяет более экономно расходовать боекомплект. Недостатками является так называемый эффект «хлыста» – ствол при выстреле испытывает на себе мощные колебания, что приводит к резкому снижению точности при стрельбе очередью. Данный недостаток решается помещением стола в направляющие (БМД-4 и БМП-3) или сильным снижением темпа стрельбы (БТР-80А)

    Translation:

    For example, in one of the works chosen was 30-mm gun 2A72 widely used in the army. The advantage of this gun is selective feed and reliability. Gun has a low rate of fire, about 400 RPM, which allows for more economical use of ammunition. The disadvantage is the so-called "whip" effect - when a shot is fired the barrel experiences powerful vibrations, which leads to a sharp reduction in accuracy when firing bursts. This disadvantage is solved by putting the barrel in guides (BMD-4 and BMP-3) or a strong decrease in rate of fire (BTR-80A).

    Yes, what Alexander Blagonravov said is absolutely correct. Low accuracy of the 2A72 was solved by putting a barrel support, but only on the BMP-3. If a 2A72 has no barrel support, it can only be fired with a "strong decrease in the rate of fire", meaning that the cost of mounting a 2A72 in a BTR-80A/82A or a BRM-3K (recon vehicle based on BMP-3 without 2A70) is a huge reduction in accuracy that is only avoided by firing slowly or by firing in single shots only. That's why the BTR-80A has three settings for the 2A72: semi-auto, 200 RPM, and 330 RPM. It says so in the technical manual (TO BTR-80A). Also, the early prototypes of early Pantsirs were equipped with dual 2A72s (unsupported barrels) instead of 2A38Ms, and the combined rate of fire from the two guns was 440 RPM, or 220 RPM each. Given this track record of ignoring the need for a barrel support on a cannon that clearly needs it, suggesting that the 2A42s on the BMPT should be replaced with 2A72s is just irresponsible.

    Anyhow, I know you like to use the Tigr-M as an example of the "low recoil" of the 2A72, so let's ask the question of how were they able to stick a 2A72 onto the roof of a small 4x4 car: No, it's not because 2A72 has such low recoil that it can be installed on a roof that is "less than 7mm thick". It's because they had to build an intrusive structural support inside the cabin to support the turret, reducing the number of passenger seats in the cabin from 7 to just 2, as you can see in the photos below.





    On the other hand, the installation of the 2A42 in an unmanned turret in the Typhoon-VDV had a much, much less effect on the inhabitable space inside the car.



    kopyo-21 wrote:
    PS 1: BTW, you should revise the data about firing accuracy of 2A42 in your blog. The given data is totally incorrect that may makes you and your readers percept wrongly not only about 2A42 bust also about 2A72.

    PS 2: The 2A42 is nothing better than the 2A72 (with barrel's rigid sleeve support) but only ROF.

    PS 3: In the contrasts, the 2A42 is bigger, more expensive, smockier and much more recoil than the 2A72.

    PS 4: Sofar, you still can not prove anything that you use to fight back my points, suggest replacing the 2A42 by 2A72 on new generation of BMPT.


    1. Laughing

    2.  Laughing

    3.  Laughing

    4.  Laughing  Laughing  Laughing  Laughing  Laughing


    Your proposal to mount two 2A72s to replace the two 2A42s and increase the firerate of the 2A72s "with some modifications" demonstrates a total lack of understanding of the mechanism of the 2A72. The long-recoil action limits its fire rate to around 330 RPM, and the cannon fires at its maximum RPM at all times. It cannot go any faster.


    Last edited by Interlinked on Fri Feb 02, 2018 7:39 am; edited 2 times in total
    avatar
    GarryB

    Posts : 17213
    Points : 17819
    Join date : 2010-03-30
    Location : New Zealand

    Re: Future of Russian IFV/BMPT

    Post  GarryB on Thu Feb 01, 2018 10:32 pm

    If you look at the MG42 it is pretty clear how you could increase the rate of fire of the 2A72... the MG 42 has two different bolts... one heavy and one light... the different bolt weights offering different rates of fire.

    The 2A72 could easily be made to fire at a high rate of fire... simply have the barrel disconnect from the bolt during recoil so that it is only the bolt recoiling and not the bolt and the barrel.

    Of course this will lead to increased fumes in the crew compartment, but as most new turrets with 30mm cannon are unmanned that would not matter.

    Of course unsupported barrel and higher rate of fire and you would end up with poor accuracy and fumes in the crew compartment... you might as well have the 2A42.

    Personally I think replacing the two single barrel 30mm cannons on the BMPT with a twin barrel 2A38M, or the GSh-30-2 as mounted on the Hind and Su-25 would be a better solution... the high rate of fire could be compensated by with very short bursts of 1-20 rounds.


    _________________
    “The West won the world not by the superiority of its ideas or values or religion […] but rather by its superiority in applying organized violence. Westerners often forget this fact; non-Westerners never do.”

    ― Samuel P. Huntington, The Clash of Civilizations and the Remaking of World Order
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Fri Feb 02, 2018 6:52 am

    Garry, that's not how the 2A72 works. The barrel and bolt both recoil backwards together when a shot is fired (so the total mass of the recoiling elements is actually a bit higher than 36 kg as the weight of the barrel alone would suggest). You can't increase the rate of fire of the cannon by having bolts of different weights because the bolt is already very small and lightweight, especially compared to a 2A42 bolt, and its weight is much smaller than the recoiling barrel so increasing the weight of the bolt won't increase or decrease the momentum of the recoiling elements by much, so you won't change the rate of deceleration by much. For reference, here's a 2A72 bolt:



    As you can see, it's really quite a tiny thing compared to the size of a 30mm cartridge. The bolt is cylindrical with a rotating head and four locking lugs, and the diameter of the bolt is only a few millimeters larger than a 30mm case, and it's also shorter than a 30mm cartridge. The return spring fits into a cylindrical tunnel inside the bolt, and the firing pin is there as well, so the bolt is hollow. The weight of this bolt is absolutely insignificant compared to the 36 kg barrel even if it was made from solid steel.

    The method used on the MG 42 worked on the MG 42 because the bolt was the only recoiling element, and you could have a bolt as light as 550 grams or as heavy as 950 grams. That's almost a 100% increase in mass! If you want to reduce the rate of fire, remember that you have a recoiling barrel that weighs 36 kg on its own, so increasing the mass of your ~2 kg bolt by 100% to 4 kg will only result in a total change in mass of 5.2% (40 kg total vs 38 kg total). This will also be true if you want to increase the fire rate by decreasing the mass of the bolt, which is not an easy thing to do since it's already extremely small and light. If you can somehow manage to cut the mass by half and create 1 kg bolt, you'd only be changing the total mass by 2.7% (37 kg total vs 38 kg total). Switching the heaviest bolt for the lightest bolt to cut the mass of the recoiling elements by 50% in an MG 42 can give you a 66.7% increase in fire rate (1500 RPM vs 900 RPM), but a difference of that magnitude would only effect a 2.7% difference in the total mass of the recoiling elements. That really won't change the ROF of the cannon by any noticeable amount.

    The bolt already disconnects from the barrel during the recoil cycle, if by "disconnect" you mean unlock. The 2A72 has a rotating bolt and no real "bolt carrier" like a 2A42 (which is basically the same as an AK-47) and no delayed recoil mechanism like the FAMAS, G3 or MG 42, because it's a long recoil gun. The bolt carrier on the bolt of the 2A72 is just the rear part of the bolt. The only part that rotates is the head, with the four locking lugs.


    Last edited by Interlinked on Fri Feb 02, 2018 9:18 am; edited 2 times in total
    avatar
    Interlinked

    Posts : 136
    Points : 138
    Join date : 2017-11-07

    Re: Future of Russian IFV/BMPT

    Post  Interlinked on Fri Feb 02, 2018 7:57 am

    Here's what happens when you fire a short burst from a 2A72 in a BTR-82A. Looks like the gunner was firing at the low rate (200 RPM) or in semi auto.


    kopyo-21

    Posts : 163
    Points : 165
    Join date : 2013-08-21
    Location : Bangkok - Thailand

    Re: Future of Russian IFV/BMPT

    Post  kopyo-21 on Fri Feb 02, 2018 8:55 am

    Look back @Interlinked. I have never ever suggested to increase ROF of 2A72 . What I said and proved was, intead of firing in turn, gun by gun like 2A42 on BMPT-72, they should improve the feeding system to have both 2A72 gun fired the same round, either HEI or API, simultaneously. In that case, total their ROF is the same with a 2A42 gun.

    As mentioned, I did not care about "7 tons" and "20 tons" number so you are waste time to focus on where they come from. You write a lot but that don't help you to create your owned phisics laws, deny the Newton's conservation of momentum laws and escape from facing with the reality.

    Your informations about 2A72 gun's mechanism, out of your intention, just help to make more clearly how it spread out its recoil over 2 stages, the first 260 mm and the second 65 mm. That help you nothing to prove your points and to refuse "the longer moving back is, the less recoil force is." You are totally wrong to think that, the spreading out recoil just starts when it barrel hit the bolt and its recoil distance is just 65 mm. The correct is, it starts spreading out the recoil when moving back and its recoil distance is 325 mm, accumulated from 260 mm and 65 mm.

    You also (can not) say nothing about the light tank Sprut-SD that use longer-recoil (700 mm) to reduce much more recoil than shorter-recoil (300 mm) 2A46M gun of heavy tanks T-72/80/90.

    Back to the 2A72 gun, there are alot bullshits floating on internet about it without supportive data. Those bullshits just come from stupid netizens who just hear the rumors here and there, and easily thrashed by someones who can not digest the reality. Back to data from 1990's, the firing accuray, both HEI and API rounds, of 2A72 guns on BMP-3 and on the BMP-1 (Clever turret) is the same with 2A42 gun on BMP-2 so it is stupid to use its firing accuracy factor to deny it.

    There are some methods to improve the firing accuracy of 2A72. The first is attaching its barrel to a rigid sleeve support like BMP-3, BMP-1 "Clever", Uran-9 and Ukrainian BTR-3/4. The other is what "VPK" LLC do with BTR-82A. Instead of using the sleeve support like others, they just decrease its ROF by realizing that, the gun's barrel needs a while to recover its designed status after each firing so just simply give it enough time to recover. Finally, the 2A72 gun on BTR-82A achieves the same firing accuracy like 2A42 gun on BMP-2. Don't forget that, the BTR-82A is wheeled and achieving the same accracy of tracked BMP-2 is not easy.

    You may not know, the BTR-82A is the first and only vehicle sofar that apply the airbrush HEI round for its 2A72 gun. Therefore, although its slower down ROF, its effectiveness is still much more than others.

    Besides beeing imposible to answer why most of successfull ligh combat vehicles in both Russia and Ukraine are using 2A72 gun instead, you also can not answer why the Chelyabinsk Tractor Plant (GSKB-2) leaded by chief designer VL Vershinsky  and the Instrument Design Bureau (KBP) leaded by chief designer A. G. Shipunov chose 2A72 guns for their BMPT project "781" instead of 2A42 guns. They all were much knowledgeable and smart enought to chose the best for their project. The guns totally were instaled outside of the hull so this time was not because of the "smocky issue" anymore.


    Sponsored content

    Re: Future of Russian IFV/BMPT

    Post  Sponsored content


      Current date/time is Thu Feb 22, 2018 3:58 am