That's right, a 4 inch "power house" with 33.7mm porting. It was designed to accept many calibres, from 33.7mm down to 6mm. It is around 1.5 litres.
I tried to pilot this with a 1/4" ball valve with no success, 1/2"ball valve does well though and makes it a loud mo-fo.
I operate this at around 95 psi.
Did i mention that it leaks? I could fix the leaks but i really can't be bothered with 10psi over 20 seconds.

Boogaloo

Front on- you can see the piston face...just.

assortment of 33.7mm ammo.

piston

Bumper/endcap.











