this is a break action 37mm launcher. it uses a 1 5/8" steel tube with a 39-39.5mm ID as a barrel liner, an ar15 firing pin an AR15 FCG, an ar style push button safety (inserted upside down, with a detent, half a detent spring, held in place with a 8-32 set screw) , and a stock or pistol grip for a mossberg 500.

the only specialized part is the breach face, which is a 1/4" thick, 3/4" od rod with a 3mm hole down the center so that an ar15 firing pin can be inserted. The firing pin should have a approximately 55mm long 7.4mm OD spring to prevent it from over protruding.

the plunger needs a 5/16 2' long compression spring, the latch requires a 1/4" od 5/8" long spring to latch correctly.