The plug i purchased from
PR Bullet was not made to be used with an o-ring. They will modify your plug to use the large rifle primer adapters. It didn't seem to me i could do a nice clean job converting the PR plug to use an o-ring, nor did i wish to modify the plug, so i didn't.
What i did was take a brand new TC plug, and enlarge the flash hole to 0.032", and then i used a 7mm end mill to enlarge the primer socket so to receive the PR adapters. Using good machinery the 7mm end mill would make a hole 0.276" in diameter. However, my hobby machine has so much run out, the socket ended up at 0.281" diameter. The primer socket was also made deeper than the PR socket, so that i could use an o-ring. Recently i had a notion to enlarge the flash hole, so it is now 0.034", which i believe will work better in sub-freezing conditions.