As the man said, U.S. bayonets are married to one or two battle rifles-muzzled, as it were.
The Bowie bayonet was (one of several long blades) mated to the Krag-Jorgensen; the M1 bayonet was made to sit atop the M1 Garand; the M6 bayonet was made for the M14 rifle, and so on.
In this case, the M7 bayonet is synonymous with the M16 rifle. The M7 and the M16 went to South Vietnam-the Republic of-on the buddy system. And their partner-in-crime, the M8A1 sheath tagged along just for kicks. I am a child of the Vietnam era, a friend of the M16A1 service rifle.
I own its civilian counterpart-the AR-15. And despite a bumpy start, the M16/AR15 is alright.
The M16, Rifle, Caliber 5.56mm traces its lineage to designer Eugene Stoner and the Armalite Company. After World War II, the United States recognized its need for an infantry rifle with enhanced firepower and a greater likelihood of inflicting casualties on the enemy. But greater firepower meant grunts like me/you had to haul all that heavy brass, so a lighter service rifle with lighter ammunition became mission-critical. And in 1954, Stoner came up with the M16's older brother, the AR-10 in 7.62.
And no one wanted to carry all that heavy .308. A shame, because the AR-10 is one great gun.
The M16 is chambered for 5.56mm or, in civilian-speak, .223 caliber. This full-auto gun is air-cooled and gas-operated. And since its introduction to Vietnam in 1964, it and its variants have fared well to the present. Riding atop the M16's 38 1/2 inch frame, the M7 performed well in Southeast Asia, if only as a great pig sticker or can opener for C-rats when a guy lost his P-38.
The M7 sports a checkered black plastic grip and is virtually identical to the M6; both sport a 6.7-inch, single-edged blade. The difference between the M7 and the M6 are their muzzle ring diameters and locking mechanisms. The M7 attaches to the gun via a release at the end of the handle (pommel); the M6 has a spring-loaded lever near the guard that releases the bayonet.
The M7 blade is 6.75 inches. Overall length is 11.875 inches, with a muzzle ring diameter of .880 (the muzzle ring fits over the flash suppressor). The M6 muzzle ring diameter is .725 inches.
What's neat is the M7 can be mounted atop U.S.-issued combat shotguns like the Remington 870 and the Mossberg 500 and 590. It has been manufactured by several companies, initially Bauer Ordinance Corp., of Detroit, Rhode Island's Imperial Schrade Corp., and several foreign manufacturers.
The M7 was replaced by the M9 bayonet.
It shouldn't be hard locating an affordable M7 bayonet. There's plenty of 'em around. If you do, it will make a nice addition to your knife collection or framed and hung on the wall in your gun room.