[Steigerwald]

Originally Posted by EricH

Especially in elims, when that part that wasn't designed/built right fails suddenly because it took a load that it couldn't take.

Do it right the first time, and it'll keep going. Right, Mr. Lavery?

As for "How could a T-shirt jam?", most launched T-shirts are wrapped somehow for distance reasons. Usually, it's a rubber band or three. Guess what? Said rubber band or other wrapping has a much higher coefficient of friction than a T-shirt, and may stick in the barrel. The T-shirt then sticks too, and you suddenly have a jam. Now you have pressure that can't get the shirt out and can't go elsewhere. Your best bet in this case is to drain pressure immediately and use a stick to remove the shirt, but sometimes, it takes care of that for you, in spectacular fashion.

Well put!

The fact is that on this cannon, the barrel assembly is not made properly. The fittings are not inserted and some are not pressure rated. The need to be replaced to be safe. Period.

You asked for a way to solve the problem instead of just complaining? Fine, here you go!
Plumbing Supply
McMaster

I'll put up some pictures of what I have done which would work perfectly for your application.