My 455 American 22lr barrel is factory threaded at 16.5. Threaded the 17hmr at 18”. Gunsmith I used is a 17hmr fanatic. That was his recommendation in length, and with all the ones he has and shoots I have no reason not to trust him. Both work just fine with the dead air mask at those lengths
He said I could easily thread them at 16.5” 1/2x28
Shouldn’t be a issue honestly
