Russian 57mm AutoCannon Turret:
The Future Caliber or Relic from the Past?
The Franco-Russian cooperation for an IFV was recently revealed. It's an 8x8 vehicle called Atom.
One of the features that got quite a bit of attention is the 57mm main gun in the two-men turret.
The turret is called AU-220. It's been initially developed as an upgrade to the PT-76 amphibious tank to replace its 76mm main gun and old turret.
An upgraded PT-76 is shown with the 57mm AU-220 turret.
The 57mm gun that's also used in Atom 8x8 is basically an Anti-Aircraft gun used in S-60 towed AA system. The gun was developed in 1950's.
In the AA configuration the gun is fed by 4 round clips. The same gun in the S60 AA mount is shown below.
The same cannon also used in ZSU-57-2 SPAAG vehicle.
The cannon uses 57x347mm semi-rimmed ammunition. The image below shows the 57mm ammunition vs the Bofors 40x365 ammunition.
The gun is recoil operated. Rate of fire is 105-120 rpm and the muzzle velocity is around 1.020 m/sec. It has a barrel length of around 4.4m.
The effective firing range against ground targets is 4km's.
The turret is of Two Men configuration and weighs around 3.5 tons. The main armament is the 57mm rapid fire cannon.
The gun has a new automatic loading capable ammunition feed system that houses 20 ready-to-fire rounds as shown below.
The turret basket has a powered 73 round ammunition carousel that provides ammunition to the linkless feeder above.
The 57mm gun with the AP round has a penetration capability of 130mm of Steel at a range of 1.000m. I would expect the penetration would be much better for the huge 57mm caliber.
The 35mm APFSDS round has 120mm penetration at the same range.
This does not mean a lot at first glance, and you can think that the 57mm is still better than 35mm.
But when you think about the 35mm round doing all this with only 22% of the mass of the 57mm, one thinks that the 57mm caliber needs new ammunition in the APFSDS type to become a serious contender in the medium caliber market.