The USP is a semi-automatic pistol with a mechanically locked breech using the short recoil method of operation. 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. 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. After 3 mm (0.12 in) of unrestricted rearward travel, the projectile leaves the barrel and the gas pressures drop to a safe level. 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. 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. 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. This tapered surface produces a camming action which assists in positive lock-up in the presence of heavy fouling and debris.
One of the distinguishing features of the USP is the mechanical recoil reduction system. It consists of a short additional spring located within the main recoil spring on the breech end of the recoil spring assembly. Designed primarily to reduce wear on the pistol’s components, the system also lowers the peak recoil forces felt by the shooter. The design with two springs allows the system to work with different kinds of ammunition without requiring any adjustments. Unlike similar systems employed in other guns, the USP design does not incorporate a hydraulic damper and requires no maintenance. Using a similar recoil reduction system, the H&K Mk 23 pistol fired more than 30,000 high pressure (+P) cartridges and 6,000 proof loads without damage or excessive wear to any major components. Abuse and function-testing of USPs have seen more than 20,000 rounds of .40 S&W fired without a component failure. MILSPEC environmental tests were conducted in high and low temperatures, in mud, immersed in water and in salt spray. In one particular test, a bullet was deliberately lodged in the barrel and another bullet was fired to clear the obstruction. The barrel was successfully cleared with only minor structural deformation and continued to produce consistent groups when test fired for accuracy. The recoil reduction system is not present on the USP Compact models, which instead use a simple polymer bushing as a buffer to reduce slide on frame impact.
Major metal components on both the USP and Special Operations Pistol are corrosion-resistant. Outside metal surfaces such as the steel slide are protected by a proprietary “Hostile Environment” nitride finish. Internal metal parts, such as springs, are coated with a Dow Corning anti-corrosion chemical to reduce friction and wear.[self-published source]
The USP is composed of a total of 54 parts and is broken down into 7 major components for maintenance and cleaning: the barrel, slide, recoil spring, recoil spring guide rod, frame, slide stop and magazine. This is done by retracting the slide back to align the slide stop axis pin with the disassembly notch on the left side of the slide and withdrawing the axis pin.
There are no reviews yet.