Muzzle velocity
The APB ("Avtomaticheskiy Pistolet Besshumniy", meaning automatic silenced pistol) version was a version of the APS optimized for silent operations. Developed in the early 1970s by A.S. Neugodov (А.С. Неугодов) under the factory name AO-44, it was officially adopted in 1972 under the service name APB and given GRAU index 6P13. Approximately 2,000 APS pistols were converted to APB variants by the Vyatskie Polyansky Machine-Building Plant from 1972 to 1973. Muzzle velocity reportedly dropped to 290 m/s in this variant. Instead of the holster-stock of the APS, the APB comes with a detachable stock made of steel wire. Its barrel is longer than that of the APS; it protrudes from the slide and is threaded for the attachment of an eccentric sound suppressor. When not in use, the detachable sound suppressor can be clipped to the stock.