You could not build something similar to Pantsir-S1 with 57 mm guns,
because those guns are to large and they/it have to be placed in the
middle of the turret not at sides. For system like Tunguska or Pantsir,
30 mm gun is the best option to be placed at side, maybe 37 mm gun, but I
think 37 mm gun is no more in use in Russian military.
I agree. Without making a really huge turret two 57mm guns is too much... especially if you want a dual feed weapon with the ability to choose between two different types of rounds quickly.
57mm is enough of a jump up in power from 30mm to make the extra reach worth it.
The 35mm guns on the Gepard are not actually that much longer range than the 30mm of the Tunguska and have a fraction of their rate of fire and so rely on accuracy... which is good for straight and level targets but not for small or manoeuvring targets.
The 57mm round has an extra 2km range over the 30mm (6km vs 4km) with standard ammo and with guided ammo perhaps 8km -10km effective range.
The ability of the 57mm round to follow targets as they manoeuvre means they don't need rapid fire capability.
The 37mm round previously used by the Russians is probably not that much more effective than the 30mm as its slightly extra range advantage is negated by its reduced rate of fire.
Having said all that I think a modern telescoped round of even better performance is worth developing.
[quote]57 mm gun is excellent option to be placed on BMPs and could have air
defense as secondary role. They could also produce specialized 57 mm SP
AA gun, with radar, TI, laser rangefinder and marker, datalink, etc, to
supplement other air defense systems in ground units. It could be also
equipped with some Iglas at sides.[/qutoe]
We are in agreement... however instead of Iglas with a 6km range I would be tempted to use SOSNA missiles with an 8km range and using laser beam riding guidance.
The main fault of the 57mm laser homing shells is that their optics is pointed at the target so they are vulnerable to DIRCMs. If a laser has to be on board the vehicle anyway a few SOSNA missiles that use beam riding technology could be used while the 57mm autoloader is reloaded, and also in case the target is blinding your rounds.
Of course firing at 120 rounds per minute and remember because there is only one laser needed marking the target think of the scenario of a group of BMP-5s (made up but bear with me) with a mix of 100mm rifled 2A70 guns with 30mm cannon mounted coaxially for a range of targets and also vehicles with a single 57mm main guns as a dual purpose anti ground and anti air weapon that mixes a high rate of fire with a small HE payload and an incredibly high velocity anti armour round and of course a guided round for air and ground targets.
An enemy A-10 appears over the hill and rolls in, the first BMP with a 57mm gun and laser marker directs a beam onto the A-10 and starts firing... two other BMPs in the unit with 57mm guns also train their guns in that direction and start firing too. The A-10 detects the laser and from its intensity can tell it is being marked for laser homing rounds and its DIRCMs are activated. The system starts dazzling the rounds as they approach but with three guns firing at potentially up to 240 rounds per minute the DIRCMs system is overwhelmed and the 2kg shells start hitting the A-10...
In a second scenario lets say it is a flight of 8 Apaches in very open terrain but their DIRCMs collectively are able to deal with the number of 57mm shells being directed at them... if the BMPs fire 3-4 SOSNA missiles that DIRCMs can't do much about because the missile is travelling at over 1km/s and is looking back at the launch vehicle and not at the target then the flight numbers are suddenly reduced and the 57mm shells can overwhelm the remaining aircraft.
Obviously these two examples are idealised to show what the new air defence vehicle could do.