The Heckler and Koch Mark 23 is a semi-automatic large-frame pistol chambered in .45 ACP. HK is a German arms manufacturer founded in 1949 and is headquartered in Oberndorf am Neckar, Germany.
The MK23 was originally designed in 1991 in response to the USSOCOM Offensive Handgun Weapon System program. This competition (begun in 1989) sought to encourage the design of a pistol package that could offer the same customizable aspects and firing capabilities as longer-barreled carbines and submachine guns. The MK23 was eventually chosen over the Colt OHWS. During testing, the MK23 was able to fire tens of thousands of rounds without the need for a barrel change. Furthermore, the MK23’s test firing averaged 1.44″ groups at 25 meters, which far exceeded the US government’s requirements. In one test grouping, using a precision firing fixture, 5 rounds passed through the same hole.
The MK23 is constructed of corrosion-resistant polymer and steel. The MK23 offers a a threaded O-ring polygonal barrel, a design that is reported to increase durability and performance. The MK23 can be carried in single-action mode with the safety lever on, and features a frame mounted de-cocking lever as well as a separate ambidextrous safety lever. The MK23 is designed to reduce felt recoil, and also offers an oversized trigger guard for use with gloves.
Additional features include an ambidextrous magazine release lever, a patented Lock-Out Safety device, which disables the gun with the turn of a key, and a loaded chamber indicator that gives a visual indication that the weapon is loaded.
When used by the military, a laser aiming module and suppressor is attached to the gun.
The Mark 23 is designed for tactical and military applications. The civilian model, known simply as Mark 23, does not include the original laser aiming module (LAM) or sound suppressor.