AHawkeye bore scope would allow a very thorough inspection of the threaded area of a MZ barrel, just like we use them to inspect the throat of a CF rifle. I'm not seeing that as a big issue, though; since the main "pressure relief valve" of the system is the nipple - and even the 209 systems are somewhat leaky.

If I were T/C, I too would be hesitant to sell breech plugs because of all the folks out there who are building their own guns; andwant to try to thread and install the plug themselves. These barrel threads need to be machinedprecisely and torqued up very solid. Also, there is the issue of the flats on the barrel being indexed - and this would certainly require the services of a skilled lathe operator to shave the barrel shoulder off just enough to index under torque.

Overall, I would be surprised to find the breech plug threads worn away on a MZ barrel that has been shot a bunch. I could imagine some throat erosion on a gun that has had agadzillion 150 grain loads shot through it. And mostly crown/muzzle wear from the bullet seating process on any MZ rifle.