I wanted the drum's journal to bottom against solid steel, rather than be threaded clear through to the chamber. That way, there is less of a chance of 'gas cutting' on the threads of the drum, which eventually will jeopardize the integrity/safety of the patent breech. Also, I can remove the drum any time I want, knowing that when I return it, like a breech plug itself in a barrel, it should fit up tightly, and not overturn.
I installed the drum by wrapping it with a doubled layer of 80 grit abrasive cloth folded against itself, with the abrasive on the outside. I used a pair of vise grips, clamped up the drum once it was started in the threads, and ran it in until it bottomed firmly on both the end of the hole and the side of the flat. I recommended that the rifle maker, once he has fit the breech to his barrel, polished it to final finish, installed his drum, and then drilled his nipple seat, witness mark the side of the drum and barrel on the forward edge of the side flat.