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Return of the Arm Pistol

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Arguably the first large format AR-style pistol to hit the market is now set to make a return, no brace needed.

Firearms maverick Mack Gwinn Jr., a Vietnam-era Special Forces veteran, in the early 1970s acquired the rights to Colt-made IMP-221, a stockless, gas-operated bullpup pistol intended to provide aircrew with a compact survival gun chambered in .221 Fireball. While the Air Force had already scrapped the project, Gwinn made lemons into lemonade, adapting the design to use 5.56 NATO and accept standard AR mags, launching the Bushmaster Arm Pistol.

Bushmaster Armpistol ads started popping up in the early-1970s

The original Gwinn/Bushmaster Arm Pistol borrowed from both AR-15 and AK-47 designs, with its AR-style rotating bolt and AK-type long-stroke gas piston.

Based on the Colt IMP-221/ Air Force GUU-4/P air crew weapon originally designed at Eglin Air Force Base, the original Gwinn Firearms in Bangor, Maine produced the 5.56mm Bushmaster Arm Pistol “in limited quantities” for the USAF in the early 1970s before sending it to the consumer market. Just 20.63 inches long, the Arm Pistol had a lot of M16-style features in a very abbreviated bullpup format.

With the Arm Pistol long out of production and Bushmaster now in at least its third reincarnation since Gwinn sold the company in 1976, his son, Mack Gwinn III, has founded Maine-based Hydra Weaponry and returned a much-improved version of the design to production.

We caught up with the fine folks from Hydra at the recent 2024 NRA Annual Meetings in Dallas to “lay arm” on the new BMP-23.

Hydra feels the BMP-23 is the 5.56mm pistol that Gwinn Jr. would have built if he had access to today’s CNC machinery and technologically advanced materials.

‘Father of the PDW’ Passes: Mack Gwinn Jr, Dies at 79

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Florida-born Mack W. Gwinn, Jr., the son of a retired Army officer, joined the U.S. Army Special Forces in 1961 and served until 1972, a period that included seven deployments to Vietnam, earning several Purple Hearts and the Bronze Star in the process.

Then, on return stateside following the war, he developed the Bushmaster Arm Pistol. The concept, a pistol-sized gas piston firearm that used an intermediate round rather than a pistol caliber, could rightly be described as one of the first personal defense weapons and predated the initial crop of large format AR handguns such as the OA-93 by a generation.

Moving on from Bushmaster, Gwinn went on to take out several patents on magazines as well as design and develop concepts for numerous other firearms applications including the SSP-86 pistol (see the Magnum Research Lone Eagle), developed the QCB system that FN used for the modern M2HB/M3 .50 cal, and lots of other neat stuff.

Capt. Mack W. Gwinn, Jr. (U.S. Army, Ret.), 79, died on March 11, 2024, at the Maine Veterans’ Hospital in Togus.