OHIO ORDNANCE WORKS M240 7.62x51mm

The patented Selective Fire M240 Trigger Group is in the process of being approved for military service.

Having been introduced in 1958, the Mitrailleuse a gas (machinegun by gas) or MAG 58, the meaning is this acronym was later changed to the more suitable Mitrailleuse d’Appui General (general purpose machinegun). Now, more than fifty years later, this “Rolex” of 7.62x51mm NATO belt-fed machinegun design is used by countries the world over—including a few using unlicensed copies accomplished by reverse engineering the gun.

Ohio Ordnance Works has developed a selective fire trigger group that would allow any M240 or MAG 58 variant to fill a semi-automatic role, instantly transitioning to that of a GPMG by just changing a selector lever.

Unlike a number of successful general-purpose machine guns before it, the MAG 58 operates by a long-stroke gas piston using a toggle locking system that amounts to an inverted bolt group used in the Browning Automatic Rifle (BAR). The belt feed is a typical shuttle type, operated by a camming groove in the top of the bolt. By merely changing the feed tray, the MAG 58 will use continuous or disintegrating links. Not lightweight, the MAG 58 weighs 26 pounds without accessories.

The U.S. adopted the MAG 58 in the mid-1980’s as the M240 GPMG, and currently uses it in seven variations (including with suffixes, i.e., M240B, C, D, G, H and L—depending on which branch of the service, accessories, special applications & etc.). The M240 has all but completely replaced the M60 GPMG in the U.S. military, and is increasingly seen in the arsenals of federal and larger law enforcement agencies, especially where harbor security is a factor.

The OOW M240 Select Fire Trigger Group (above) is seen with a standard M240 full
automatic only trigger group. The OOW’s settings are clearly marked.