Tim, you knew I would chime in here. If it's an early paris barrel (pre 1977 when we bought the business), they used
standard coarse threads........5/8 x 11, or 3/4 x 10. If the threads appear to be the coarse variety, my bet would be that
it has a 5/ x 11 thread. I am basing that on the size of the barrel itself, and is probably a 45 or 50 cal. A plug to fit it
would have to be chased on a lathe. The Paris barrels that Tip Curtis has are from the second go-round of Paris, starting in about 1982, and later sold to Colerain. I think those barrels probably use the standard fine threads of
5/8 x 18, or 3/4 x 16. Jim, just because I'm a nice guy, if you send the barrel to me and pay the return shipping I'll
make and fit a new plug to your barrel.....no charge. Heck, I don't need the money, the Government's keeping me.......
Don