Thanks for all the positive feed back guys though I feel I could have been a little more specific about the components. The flares at the end are plastic 4"-to-cast-iron fittings, not 4" cast iron fittings (this thing is heavy enough).
It is a muzzle loading launcher, but plans are in the works for ...

Hi all, first time poster, first time builder. This is my first attempt at building what will soon become my paintball teams primary tank killing weapon.

Cannon
1" modified Orbit sprinkler valve
2" pressure rated PVC barrel chamber & fittings
Slidecheck/fill nipple

Body
4" PVC body
4 ...