daccel wrote:No I meant .028 wall thickness. Which gives .319 bore, and 5/16 ammo is .313, so a nice fit.
OK, I got it now, "3/8" with the wall thickness into account.
That will probably work.
I am pretty beat right now.(Just got back from a weekend road trip on my Harley-Davidson, It's an awesome cruiser, but halfway through, a bunch of my bolts rattled loose...little by little, everything is getting loctite'd

) Probably TMI but that's my excuse, besides I got sunburned like a lobster.
... those slingshot shot have flat sides, it's what I used in my first cannon a few years ago. Still managed to put 'em flush into a 2x4 with the help of a 6' barrel, though 8).
I added a .25 brass barrel sleeved into lamppipe barrel to a paintball gun bolt, had a magazine design ready to add, but was very disappointed with the .25 ammo on my first (or one of first) projects. It only imbedded them into a phone book.

8)