[MrForbes]

looks good!

We discovered that it does not really take much air (or CO2) pressure to fire a T shirt. The trick seems to be having the right size of reservoir, and a very large valve to quickly dump it into the barrel. Also having the smallest size barrel possible helps.

30 psi in a 200 cubic inch (2 ft of 3" ABS) reservoir, going through a 1" gate valve into a 2-1/2" PVC barrel, seems to shoot a shirt as far as it needs to go.