Found a solenoid at princess auto, will it’s specs be high enough for a tshirt cannon?
Specs are fine for safety. The only question is whether 1/2" is a big enough bore to get the flow for the shooting range you desire.
Yeah, how far could 1/2" go?
You could find a larger manual butterfly valve (or some other kind of valve) and mate the handle/actuator to a motor or a pneumatic cylinder controlled by a smaller solenoid. Assuming you already have a solenoid and cylinder, It could end up being cheaper in the end.
How about 200 psi and 1" inner diameter. Its cv factor 14 if that helps.