SpudFiles

I am currently working on a new piston gun (my first piston gun), and I was wondering how I can get the barrel inside the chamber? THe gun is all metal so there aren't any fittings I could find to do so, I am mainly asking mitch. because my cannon is based off of his designs. What could I use?

What i did (and probably mitch) was grind out the stop in a compression fitting. be sure to get it all though, or it'l be crooked.