

The design with two springs allows the system to work with different kinds of ammunition without requiring any adjustments. Designed primarily to reduce wear on the pistol's components, the system also lowers the peak recoil forces felt by the shooter. It consists of a short additional spring located within the main recoil spring on the breech end of the recoil spring assembly. One of the distinguishing features of the USP is the mechanical recoil reduction system. This tapered surface produces a camming action which assists in positive lock-up in the presence of heavy fouling and debris. For enhanced reliability in high-dust environments, the locking surface on the front top of the barrel's locking lug is tapered with a forward slope. The recoil spring assembly is held in place by the slide stop lever's axis pin and a round cut-out at the front of the slide. A shaped lug on the underside of the barrel chamber comes into contact with a hooked locking block at the end of the steel recoil spring guide rod, lowering the rear end of the barrel and stopping the barrel's rearward movement. After 3 mm (0.12 in) of unrestricted rearward travel, the projectile leaves the barrel and the gas pressures drop to a safe level.

When a cartridge is fired, pressures generated by the ignited powder drive the cartridge casing back against the breech face on the slide, driving back both the barrel and slide as they remain locked together in the manner described above. This rather conventional lock-up system has a large rectangular lug over the barrel's chamber that rides into and engages the ejection port cut-out in the slide. The USP is a semi-automatic pistol with a mechanically locked breech using the short recoil method of operation. In contrast to the P7, P9S, and VP70Z designs, the USP uses a more conventional Browning-style cam-locked action, similar to that used in the Hi-Power, but with a polymer frame.

40 S&W cartridge, followed soon by the USP9 (using the 9×19mm Parabellum cartridge), and in May 1995-the USP45 (caliber. The USP was formally introduced in January 1993 with the USP40 model (the base version) chambered for the increasingly popular. The USP prototypes were then refined in 1992, based on input from the OHWS trials, and the design was finalized in December of the same year.
#Hk usp compact 9mm magazine mod
Special Operations Command (USSOCOM), which would later result in the Mk 23 Mod 0. USP prototypes participated in rigorous testing alongside H&K's entry in the Offensive Handgun Weapon System (OHWS) program requested by the U.S. Design work on a new family of pistols commenced in September 1989, focused primarily on the United States commercial and law enforcement markets.
