Staff Writer (Updated: 8/9/2016):
Utilizing feedback from law enforcement and military personnel during its development, HK took a Browning-designed cam breech locking mechanism and mated it with their own patented recoil-reduction system while shrouding the critical internals in anti-corrosion metal and utilizing lightweight polymer construction where possible. The recoil reduction system aids in overall accuracy and lessens structural fatigue of parts while the use of plastics reduces carrying fatigue and handling weight. The pistol sports an easy-to-manage combo safety/decocking lever along the left side of the frame though this installation can be handily flipped over to the right side as the use requires. The trigger action can also be customized to suit the firer's taste through available double-action-only or combo double-action/single-action functions. The overall design is much in line with other semi-automatic handgun offerings, with many relating back to the original excellent Browning M1911 series including the widely-accepted ribbed rear frame sides for the gripping of the slide. The hammer is partially exposed at the rear of the frame and magazines are loaded into the pistol grip in the usual way. The magazine release lever is ambidextrous and a laser aiming module (LAM) or tactical flashlight can be affixed as optional accessories to the forward underside of the frame. A Picatinny rail is available for tactical models for mounting optics over, alongside and under the frame. The original USP line was marketed in three distinct popular chamberings - .40 S&W, 9x19mm Parabellum and .45 ACP. The .40 S&W design was the original USP chambering (as the USP40) and this was then closely followed by the USP9 of 9mm chambering to which then the USP45, with its .45 ACP cartridge support, was unveiled. Special versions utilize the .357 SIG cartridge (USP Compact).
The USP has since been developed into several major production forms - the base USP pistol, the USP Compact (small frame model), the USP Tactical, the USP Compact Tactical the USP Expert, the USP Match, the USP Elite, the USP Combat Competition and the P8 (German Army designation). A government agency model incorporates a double-action system sans the control lever for manual safety/decocking. The USP Tactical is a compact version of the basic USP design with the specialized features of the special forces-minded SOCOM Mark 23 pistol series. These differ visually by a portion of barrel extending past the front end of the frame for installation of a sound suppressor. The USP Compact Tactical is for US Special Forces use and sports a threaded barrel end for a sound suppressor within a compact .45 ACP frame.
The weapon - in its varied forms and at various defense group levels - has since been adopted by Albania, Australia, Cyprus, Denmark, Estonia, France, Germany, Greece, Ireland, Lithuania, Luxembourg, Malaysia, Poland (GROM special forces), Portugal, Singapore, South Africa, Spain, the United States and Uruguay.