It looks like we have 3 different 57mm guns.
Be aware that if you take the muzzle brake of a 2A42 30mm cannon and it will look like a different gun too.
The one on the Kurganets is a low pressure and low velocity gun.
I don't think there is a low pressure low velocity 57mm gun design...
The one on the Derivatsya is high pressure, high velocity gun with high rate of fire.
The gun on the T15 is probably a variant of the Derivatsya's gun with perhaps a lower rate of fire.
I would think anti armour and anti ground target and anti aircraft ammo is probably shared by both guns and that the two guns are actually one and the same.
I think the real difference is that the gun on the AA gun has a water cooling system like that fitted to Shilka and Tunguska and it also has a muzzle break to reduce recoil to reduce unwanted dispersion and also contain coil rings for setting fuses as the rounds are fired.
The twin barrel gun on the Tunguska and new Pantsir has a tube to isolate the shell from one barrel and a ring to measure muzzle velocity with the other barrel... with a single barrel you would just need the rings.
The 57mm APFSDS ROUND we have seen displayed is most likely to be used by the last 2 guns. The one on the KURGANETS is unlikely to use that round.
I suspect there are two types of ammo... one is a grenade launcher like round that is all HE projectile and a tiny stub propellent case like a shrunk down 100mm 2A80 round from a BMP-3, and the other is a bottle shaped S-60 AA gun round that looks like a standard 5.45 x 39mm rifle round but obviously scaled up.
Both would have APFSDS rounds for anti armour use and both will likely be fitted to BMP variants of the new vehicle families... the S-60 round would need to be used in the AA guns too because the slow grenade type HE round would not be suitable for air targets... yet fine for ground targets.
the vehicles are bigger and heavier the armour and armament will be better, however the larger the vehicle the more its a target, BTR-80 is seeing the biggest increase in weight and size. this is really a big change and upgrade for the armed forces
With modern computerise fire control systems and stabilised aiming systems I suspect they realise being a small target is not the advantage it used to be... being bigger but more comfortable for the troops and crew and carrying a reasonable amount of ammo is likely more use.
- First one is the LShO-57 grenade launcher with the reduced ballistic HE and APFSDS rounds that were shown next to it
As shown on that table in the photo the round to the left labelled 30F91 is the big 57mm grenade HE round with a huge projectile and tiny stub propellent like a 30mm grenade round. The centre front of the table labelled 3BM76 is the APFSDS projectile and sabot, and to the right of that at the front of the table is that sabot and projectile in a 57mm shell case the same dimensions as the 57mm grenade round on the left.
APFSDS needs high pressure and high velocity to be effective so therefore the grenade launcher that fires this round fires the HE round as a low velocity grenade and the APFSDS as a high speed anti armour round.
The other ammo is based on the 57mm S-60 shell which is a bottlenecked high velocity AA round in use since WWII... it is not the same as the ground based anti tank gun ZIS-3 which is a 57 x 480mm round... it uses the same round the 57mm ZSU-57-2 and naval 57mm guns as well.
This was made redundant as an AA round because the low rate of fire, but modern fire control systems and laser range finders and being a round big enough that it can take both a decent HE charge and a proximity fuse it have been revived because it is big enough for guided shells and airburst shells mean small targets and manouvering targets can be engaged.
Very simply a large manouvering target would take enormous numbers of round fired at it to hit it... with small calibre rounds like 23mm and 30mm rounds that was OK because their high rate of fire meant the fire control system could calculate a box of where the target will be. If you think about it a plane can accelerate or decellerate or climb or descend or turn left or right or it can do any combination of those things between the time you fire and when the rounds impact the target.
Higher muzzle velocity reduces the amount of time the target has to manouver and makes the maths easier, but lets reduce it down further. You have a pistol and 5m away is a person. In the half a second the bullet from your pistol takes to leave the muzzle and impact the target how far could the target possibly move.
Dodging bullets only works in the movies.
For an aircraft that can manouver the box into which the plane will be when the shells gets there could be quite big, but a 2 second burst of shells from a Shilka or Tunguska means there could be hundreds of shells filling all around the box... with a full sized aircraft you should get a few hits and the damage they cause will make the target less agile and a more easy target for the next burst.
The problem for Tunguska is a very small target like a hand held drone even just hovering still needs to be hit so hovering at 4km it will be hard to detect and you might fire burst after burst and not actually hit it. Having airburst shells that explode as the approach the target however means that instead of 200 or 300 shells blowing past you would have 20-30 shells and they would be exploding near the drone and showering it with tens of thousands of fragments which will bring it down.
Airburst 57mm shells could reach out much further and be fitted with proper proximity fuses so if the rounds are getting closer and closer they wont explode until they are going past so they will explode much closer to the target doing more damage.
To have decent range with air burst HE rounds you don't want a low velocity grenade like round with a small propellent stub and low velocity. You want a mid sized HE round with good velocity to reach out to distant targets... like a HE round for the S-60 gun.
For an IFV that is dealing with armour and soft targets then you want the biggest HE shell you can manage but also a high velocity APFSDS round as well which is what this grenade launcher seems to be offering.
My guess is that they will mix 57mm grenade launcher armed IFVS and 57mm high velocity gun armed IFVS like they did with BMP (73mm) and BMP-2s (30mm)... because they would compliment each other.
Air defence gun vehicles would need the high velocity 57mm gun to be effective.
Note even the BMP-2M upgrade includes both the 30mm auto cannon in 30 x 165mm calibre and the 30 x 19mm grenade launcher too.
- Second and third are the same cannon (2A91, though I have seen it referred as BM-57 too), in two different AU-220M variants with different rate of fire and ammo amount but same ballistic performance.
Thanks... 2A91 57mm cannon is what we are talking about for the high velocity AA gun.
I wonder what the 2Axx number is for the 57mm grenade launcher. 2A7 and 2A14 are for the 23mm cannon, and 2A42 and 2A72 are single barrel 30mm cannon for the BMP-2 and BMP-3 respectively and the 2A38M is the twin barrel 30mm gun for the Tunguska and Pantsir-S1...
On Derivatsia and T-15 is the same gun. Derivatsia only have programing device on muzzle break to program air burst programable ammunition. It would be good to equip T-15 with air burst ammunuition as well.
With the 30mm airburst ammo there is a rear looking optical sensor in the 30mm round and a coded laser beam is used to set off the round from the vehicle that fired the round... it means no expensive accurate timer is needed in the shells which makes them vastly cheaper... I would hope the 57mm airburst rounds would be the same to be honest. Note the Tunguska has an induction coil over one muzzle to measure muzzle velocity in real time which is passed to the fire control computer to improve accuracy... are you sure it is not doing this?
Kurganets with low pressure gun could not use APFSDS ammunition, because APFSDS have even higher pressure than ordinary ammunition
But the ammo displayed on the table shows both a HE round and an APFSDS round.
No one said the 57mm grenade launcher was a low pressure weapon.
The APFSDS rounds on display show it is not a low pressure weapon.
Low pressure gun need special ammunition with less powder in it and could not use the same ammunition as derivatsia and T-15.
The only low pressure guns they use are the 73mm gun of the BMP which is more a closed end recoilless rifle like an SPG-9, and the 30mm and 40mm grenade launchers.