for M1 Rifle
BRIEF OVERALL HISTORY
The M7 was the first rifle grenade launcher adopted for the M1 Rifle. While spigot type rifle grenade launchers had been developed for previous rifles, the M1 Rifle presented a new challenge with its semi automatic function. Merely placing a launcher on the muzzle would over gas the operating system likely causing injury and failure of the rifle. A way to vent excess gas was needed. This was done by the adoption of a vented gas cylinder lock screw that was opened when the launcher was attached. This new lock screw and the M7 launcher would be adopted in 1943 and serve through WWII.
This launcher was made by Knapp-Monarch (KM), which is marked on the underside of the latch arm along with the model (M-7 Launcher) and what rifle it was for. Interestingly, Knapp-Monarch was a small appliance manufacture, making things such as irons, toasters, and fans.
The numbers 2 through 6 mark position rings on the launcher. These are used in determining range along with the angle of the launcher and the type of munition. The numbers correspond with the inset ring above each number.