Thanks for the Help everyone

I have been to a auto parts store. Could not find any SAE or metric thread to fit. It appears to be about 5/8 in diameter. Yes I found on the Lyman site and others that they sell an adapter to fit the regular 7/8-14 coarse thread, but I would need the inside thread of the adapter. I have sent an ema...

It's not like any bolt thread. I don't know if there is a machinist thread or something else

I have rather an odd, I suppose request. I am looking for where I can purchase The round nuts that go on the powder drop tubes. They must be a different kind of thread, because I cant seem to match them up to any bolt size. I would like find 3 or 4. Thanks much