The S4M (Russian: С4М) was a Soviet insurgency weapon pistol, designed to be used expressly for the purpose of assassination. It was a simple break-open, two-shot derringer, but the unique features came from its specialized ammunition, designed around a cut-down version of the 7.62×39mm rounds used in the Soviet AK-47. The casings of the round contained a piston-like plunger between the bullet and the powder that would move forward inside the casing when fired. The piston would push the round down the barrel and plug the end of the casing, completely sealing off any explosive gases in the casing. This, combined with the inherently low-velocity round resulted in a truly silent pistol. The nature of the gun and ammunition led to it being wildly inaccurate outside of point-blank range. To add