Odd Ones Out: Experimental and Unorthodox Firearms from the Girardoni to the XM25

The Girardoni air rifle was engineered around 1779 for the Austrian army. A tubular magazine held twenty to twenty two lead balls, and a reservoir of compressed air gave roughly thirty shots on one charge. Meriwether Lewis carried one on the Lewis and Clark Expedition and used it to show that it could shoot so often and without powder.

Hugo Borchardt designed this pistol in 1893 using the toggle lock of the Maxim gun for a locked breech, short recoil action. He also created the bottlenecked 7.65x25mm cartridge for it. Ludwig Loewe and Company built about 1,100 and Deutsche Waffen- und Munitionsfabriken nearly 2,000 more, making it the first mass produced semi-automatic toggle action pistol.

Melvin Johnson designed this short recoil semi-automatic rifle in .30-06 Springfield, produced from 1940 to 1945. It competed unsuccessfully against the M1 Garand for adoption as the standard American service rifle, and saw only limited use with United States Marines during the war.

George Hyde designed this single-shot .45 ACP pistol, and the Guide Lamp Division of General Motors built about one million over a few weeks in mid-1942 at roughly two dollars each. It was meant for resistance fighters in occupied territory, but most were never issued, and Allied forces destroyed much of the surviving stock after the war.

William G. De Lisle built this British carbine around an integrated suppressor and subsonic .45 ACP ammunition, and writers describe it as one of the quietest firearms ever made. Only 129 were manufactured, seventeen prototypes by Ford at Dagenham and the rest by Sterling Armaments, and it went only to specialist units on clandestine operations.

Robert Mainhardt and Art Biehl of MB Associates developed the Gyrojet in the 1960s. It launches small rockets called Microjets rather than bullets, so it needs no heavy barrel to contain pressure and produces little recoil. Velocity was very low at the muzzle, reaching around 1,250 feet per second only after about 30 feet of flight. It was produced from 1962 to 1975.

Vladimir Simonov designed this Soviet rifle in the early 1970s, and it was adopted in 1975. It fires steel flechettes from an unrifled barrel and relies on hydrodynamic effects to keep them stable underwater, which makes it markedly less accurate when fired in air.

The Avtomat Nikonova model of 1994 was designed by Gennadiy Nikonov between 1980 and 1994 as a prospective replacement for the AK-74 series. Its signature feature fires two rounds before the shooter feels recoil, with a stated cyclic rate of 1,800 rounds per minute in that mode. Complexity and cost kept it a specialized weapon in limited numbers.

Vasily Gryazev developed this designated marksman rifle at the KBP Instrument Design Bureau as a variant of the 9A-91, chambered in 9x39mm. It was conceived as a cheaper alternative to the VSS Vintorez, firing a similar heavy subsonic round, but its suppressor is a separate unit rather than part of the barrel assembly. It entered service in 1994.

Designed by Heckler and Koch with Orbital ATK, this bullpup grenade launcher fired programmable 25x40mm airburst ammunition. It was fielded for evaluation in Afghanistan from 2010, but malfunctions and 2013 budget cuts delayed entry into service, and the United States Army terminated the program on July 24, 2018.