No recent wiki edits to this page.
The USP currently comes chambered in 4 different calibers: .45 ACP, .40 S&W, .357 SIG and 9mm Parabellum.
The USP was designed at the same time as the H&K SOCOM MK23, and as a result, it underwent much of the same testing for ruggedness and reliability. It was tested by being frozen at -47 ºC (-52.6 ºF), fired, frozen again and then heated up to 67 ºC (152.6 ºF) and fired again. These tests were meant to strain the metal to it's maximum, yet it passed the tests repeatedly without problems. The USP was successfully deployed by German Navy combat divers for 2 years without the adverse effects of corrosion, as well as being subjected to the rigorous NATO MIL-SPEC mud and rain tests.
The USP is currently used in the Estonian Armed Forces, Irish Defense Forces and other military and police groups around the world.
The USP slide is covered with an extremely hard nitro-gas carburized and black oxidized finish. The barrel of the USP is cold-hammer forged from high-grade chromium steel. The fiber-reinforced polymer frame is stiffened by stainless steel inserts at areas subject to stress and friction. It uses the Browning-style cam-locked of the M1911 and Hi-Power pistols.
Some minor differences between the USP and the 1911 are that: the thumb safety also acts as a decocker; the magazine release lever is ambidextrous; and there is an available optional unique LEM (Law Enforcement Modification) trigger. It has a proprietary sized rail in the front of the frame, and mounting accessories that are not tailored for this gun is impossible without a picatinny rail adapter. The most common upgrades that USP's get are what's called a "mag funnel". This apparatus attaches to the mag well and acts similar to competition main spring housing found on modern M1911 pistols. While using mag funnels, standard magazines can be used, as well as extended magazines that fit flush.