Zivo Sun Feb 01, 2015 9:54 pm
Well, there's no Soviet 57mm APFSDS round. The AP variant is nothing to scoff at, but it's inefficient for its size compared to modern armor piercing munitions. Even so, if you were to field a BMP using the old AP rounds, it would still be better armed than 99% of all BMPs out there. Fortunately developing a APFSDS round based on the conventional 57mm round wouldn't be much of a challenge.
About telescopic rounds, they're not without their problems, so I wouldn't be so quick to jump on the CTA bandwagon.
To maintain ballistic parity with conventional ammo of the same caliber, the propellant load is notably higher and has to be densely packed around the projectile by a increased factor of almost 1/3 vs conventional rounds. As such, their burn is less efficient and dirtier. They produce higher heat, significantly degrading barrel life and increasing the probability of barrel failure. While the round is easier for mechanized handling, its' larger diameter and heavier compared to rounds of the same caliber and performance. The gap between the round case and the cone of the barrel permits blowby of the propellant gas similar to the gap between the cylinder and forcing cone of a revolver, further decreasing efficiency. On top of that, telescopic rounds are more expensive to manufacturer.
It's not all candy and roses, you end up trading raw performance, cost, and service life for improved ammo handling.
From the DOD: http://www.dodig.mil/Audit/reports/FY96/96-164.pdf
IMO it's smarter to stick to upgrading the current 57mm round with better projectiles. Make a long range, hard hitting APFSDS round, and a laser guided HE round with a decently sized warhead. Keep the ballistic performance, and count on the unmanned turrets to increase the spacial efficiency of the vehicle.