The original grenade launcher for the M1 rifle consisted of a snap-on muzzle device that attached to the bayonet lug, with a tube spout that provides a slip-fit for the tailboom of the grenade. The gas mechanism of the rifle was disabled for grenade launching, since it was strictly a single-shot affair. Grenade launching cartridges were single-loaded, not clip-fed.
The sight was made compatible with rifle grenades also used on the the Springfield 1903 rifle launcher and the M1 Carbine. The sight device was a pressed-steel accessory that attached to the left sife of the stock near the clip release with wood screws. It's rather crude, and designed only for a couple hundred yards range. This system was used throughout WWII and Korea until replaced by the more effective M14 rifle grenade launcher and the M79 launchers in the late 1950's.
The grenades were launched using special GRENADE LAUNCHING blanks, not the regular noise-and-flash training blanks.
It's probably NOT a good idea to try to make your own grenade launching blanks, because even the military with it's extensive experience in using blank ammo for training has experienced damaged rifles (and shooters) using blank ammunition.
Many of these items are still widely available in army surplus stores and military surplus dealers. Check the Shotgun News ads.
Please be advised that some states recently enacted legislation that made possession of the launcher/rifle combination an "assault weapon" with the related ownership problems. Possession of real explosive grenades of course is prohibited. WWII reenactors like these rigs because it was common for one designated rifleman in an infantry squad to be the grenadier.
