WB
I'd not use plastic pipe! Metal with threaded breach.
Thursday, June 28, 2018, 19:12

And absolutely no bore obstruction or projectile. Pressures skyrocket and are super erratic if there is an airspace between the explosion and obstruction.

I remember seeing an old Val Forgett article where they filled a .58 cal ML barrel completely full of FFg, 28" of it then seated the bullet. Set it off and it held together. Then they put a charge in it and short seated the bullet. It blew like dynamite. Not exactly on topic but a lesson in the physics. I'd look for proven formal plans and instructions you can trust from a good source.

Now I'm heck with a schedule 40 PVC potato cannon and some hairspray....