proditto
Well-Known Member
API in the Sterling SMG
On some days it seems a miracle that API and Simple blow-back weapons work at all. Different proj weights, different burn rate and /or charge weight and different case brass. On experiments with the Sterling a number of interesting results were observed. As has been said the gun fires when the case stops moving forward but the bolt still is. The timing of the point is governed by the chamber depth. Using a number of different chamber depths it was possible to alter the timing. The problem was a ring bulge at the base of the cartridge case on firing a particular make of ammunition. The bolt was opening early. The concept of API was proved conclusively by altering the chamber depth and thus the timing. The problem was cured by a change in chamber depth. The propellant was very fast burning and this had altered the timing. A problem of short recoil with another make of ammo was also cured.
On some days it seems a miracle that API and Simple blow-back weapons work at all. Different proj weights, different burn rate and /or charge weight and different case brass. On experiments with the Sterling a number of interesting results were observed. As has been said the gun fires when the case stops moving forward but the bolt still is. The timing of the point is governed by the chamber depth. Using a number of different chamber depths it was possible to alter the timing. The problem was a ring bulge at the base of the cartridge case on firing a particular make of ammunition. The bolt was opening early. The concept of API was proved conclusively by altering the chamber depth and thus the timing. The problem was cured by a change in chamber depth. The propellant was very fast burning and this had altered the timing. A problem of short recoil with another make of ammo was also cured.