"Comrade Lyadov proposes a super-speedy anti-tank rifle, where the propellant burns as fast as possible, and the bullet is propelled primarily through adiabatic expansion of gases. In order to achieve acceptable pressures, the inventor uses low propellant density. With heavy projectiles, the inventor hopes to maximize the Pcp/Pm ratio and achieve muzzle velocity of 3400 m/s.
In order to achieve a chamber large enough, which the inventor says will need to be bigger than the size of the rifled section of the gun, the inventor proposes a two-piece chamber. One of them is a regular chamber, another, connected to the first, is underneath the barrel. The propellant, as can be assumed from the proposal, all fits in the first chamber."
3400 m/s! Pretty impressive. Of course, there is always a catch.
"When evaluating comrade Litvinov's proposal, it must be noted that the aforementioned muzzle velocity (3400 m/s) was obtained after making critical mistakes in the calculations, which makes the ballistic portion of his project a sad misunderstanding."