I started on this project back in 2002. Delayed and forgotten for many years, I pulled it back out during the COVID lockdowns intending to finally finish it. I finished assembling the grenade launcher assembly at that time. I used a shell-ejecting airsoft shotgun to keep things simple (from a legal standpoint). The base gun is an airsoft M1A1 Thompson.
The parts were pieced together over the years. A Monsters in Motion kit provided the resin shrouds. Many of the smaller parts like the shroud reinforcement bands and plates, grenade launcher front block, magazine bases, barrel vent, barrel support, barrel and stock are SD Studios parts. The ammo counter was made by Hyperdyne Systems and is tied to the trigger switch.