When Heckler & Koch introduced the USP in 1993, it marked the first time HK chose to incorporate many traditional handgun design elements, such as elements of John Browning's M1911, in one pistol. Two principles guided its development — the first being the use of molded polymer material, and the second being the creation of a "pistol paradigm". The HK USP is the first HK pistol designed especially for American shooters. Features favored by U.S. law enforcement and military users also influenced the design criteria for the USP.

All USPs use a fiber-reinforced polymer frame stiffened by stainless steel inserts at areas subject to stress and friction. HK pioneered this use of polymer materials in the production of handguns more than 30 years ago with the development of the VP70Z and P9S pistols.

The control lever, a combination safety and decocking lever, is frame mounted and quickly accessible, unlike the slide mounted safeties common on many semi-automatic pistols.

One of the most important features of the USP is the mechanical recoil reduction system. This system is incorporated into the recoil/buffer spring assembly, located below the barrel. Designed primarily to buffer the slide and barrel and reduce recoil effects on the pistol components, the system also lowers the recoil forces felt by the shooter. The USP recoil reduction system is insensitive to ammunition types and does not require adjustment or maintenance. It functions effectively in all USP models. Using this same recoil reduction system, one of the related HK MK23 .45 ACP Special Operations Pistols fired more than 30,000 +P cartridges and 6,000 proof loads without damage to any major components. Abuse and function-testing of USPs have seen more than 24,000 rounds fired without a component failure.

The modular design of the USP's internal components allows the control lever function to be switched from the left to the right side of the pistol for left-handed shooters. The USP can also be converted from one type of trigger firing mode to another. This includes combination double-action and single-action (DA/SA) modes and double action only (DAO) modes.

The USP was originally built in .40 S&W and 9 mm Parabellum models, but later evolved into a .45 ACP variant and later spawned the USP Compact series, which is available in 9 mm Parabellum, .40 S&W, .45 ACP, and, exclusively to the Compact model, .357 SIG. Other variants of the standard USP include the USP Tactical, USP Expert, USP Match, and USP Elite. The USP is available in nine trigger/firing mode configurations and three calibers. 9mm, .40 S&W and .45 ACP.

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 nitro-gas carburized black oxide finish. Internal metal parts, such as springs, are coated with an anti-corrosion chemical to reduce friction and wear.

The USP is the base of the Mk 23 Mod 0, a .45 ACP handgun designed by Heckler & Koch for the USSOCOM. The frame and slide of the USP45 are slightly larger than those found on the USP40 and USP9, much like the Mk 23. The prominent oversized trigger guard allows the use of gloves when firing.

Features:
* Corrosion proof fiber reinforced polymer frame
* Polygonal bore for increased velocity, easier cleaning and longer life
* Can be converted to any of nine trigger firing modes
* Patented HK recoil reduction system
* corrosion resistant "Hostile Environment" blued finish
* Oversize trigger guard for use with gloves
* One piece machined steel slide
* Universal mounting grooves for installing accessories
* Ambidextrous magazine release lever
* Extended slide release
* Patented Lock-Out safety device
* Lifetime warranty

USP

One of the remarkable features of the USP is the wide variety of the trigger styles available, which may be quickly swapped. There are nine commercially available modifications (called "variants" by HK).

By using a modular approach to the internal components, the control functions of the USP can be switched from the left to the right side of the pistol for left handed shooters. The USP can also be converted from one type of trigger/firing mode to another. This includes combination of double-action and single-action (DA/SA) modes and double-action only (DAO) modes.

In addition to a wide selection of trigger/firing modes, the USP has an ambidextrous magazine release lever that is shielded by the trigger guard from inadvertent actuation. The rear of the USP grip is stepped, and combines well with the tapered magazine, making magazine changes faster due to lack of user-assisted guiding. Finger recesses in the grip frame also aid in magazine removal. On 9 mm and .40 caliber USPs, magazines are constructed of polymer reinforced with stainless steel. Magazines on the USP .45 are all-metal. All USP magazines will drop free of the pistol frame when the magazine release is depressed. Also, the USP does not have a magazine lockout feature — it is possible to fire a chambered round even with the magazine removed. An extended slide release lever is positioned to allow easy operation without changing the grip of the shooting hand.

Variant 1 and 2 (double action/single action, decocking and safety lever)

Variants 1 (lever on left)and 2 (lever on right) allow the user to carry the pistol in a single-action mode (cocked and locked) with the manual safety engaged. This same pistol, without modification, can be carried in double-action mode, with or without the manual safety engaged, and with the benefit of a decock lever.

Variants 3 and 4 (double action/single action, decocking lever, but no safety)

Variants 3 (lever on left) and 4 (lever on right) provide the user with a frame-mounted decocking lever that does not have the "safe" position. This combination only allows the hammer to be lowered from SA position to DA position. It does not provide the "safe" position to prevent the pistol from firing when the trigger is pulled.

Variants 5 and 6 (double action only, with safety lever)

For the double action only user, variants 5 (lever on left), 6 (lever on right), and of the USP operate as double action only pistols with a bobbed hammer always returning to the DA position (forward) after each shot is fired. To fire each shot, the trigger must be pulled through the smooth DA trigger pull. Variants 5 and 6 have a manual safety lever.

Variants 7 (double action only, no control lever)

No control lever is provided on variant 7.

Variants 8 and 9 (double action/single action, safety lever, but no decocking)

Variants 8 (lever on left) and 9 (lever on right) allow the shooter to carry the pistol in a single-action mode (cocked and locked) with the manual safety engaged. This same pistol, without modification, can be carried in double-action mode (hammer down), with or without the manual safety engaged. The single action mode offers a second strike/double action capability in case of a misfire. The control lever has no decocking function on variants 8 and 9.

The USP frame is now available in several different color combinations including: tan, black and grey.

USP Compact

The first USP Compact models appeared in 1994. These are scaled-down USPs, and are available in all the same cartridges as the full size version, and additionally the .357 SIG. Due to the smaller size of the frame, magazines for the Compact variant may have a handgrip extension to better accommodate the shooter's hand. USP Compact models lack the mechanical recoil reduction system of the larger full sized USP pistols. Instead, a more compact recoil buffering system is composed of a polymer bushing, around the captive recoil spring, which is designed to absorb energy at the end of the slide's travel rearward. This polymer bushing, with an estimated lifespan of around 10,000 rounds, is used instead of the double spring/captive recoil spring/guide rod found in the full sized USP.

In addition to the Variants previously described for the full size USP, an ambidextrous safety is available from the manufacturer as a separate part. After installation by a competent gunsmith the USP Compact effectively becomes a right or left-handed firearm with respect to the decocker and manual safety functions.

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