Dave,
I get calls from customers on a very regular basis about threading. It is sometimes hard to make people understand the importance of correct threading, as this is the only guarantee that the moderator will fit correctly and alignment will not be compromised.
While on holiday at the end of last year I received a call from a customer in a bit of a panic, as he had bought two Quicksilver titanium moderators - .270 and .308 - and while checking the zero on both rifles he realised that he had shot the .308 rifle with the .270 moderator on. I asked him to send it back for a check. On initial inspection there was nothing wrong with the moderator, but just to be on the safe side I had it opened and checked all the internal components only to find that the .308 round had gone through the 8 baffles without touching a single one or the exit cap. The bore on the .270 moderator is .310" and the .308 bullet is just just that, i.e. .308" in diameter. Because of the precision engineering and perfect alignment in our products, and the excellent thread job by Mike Norris, that moderator wasn't damaged, much to the customer's relief.
I think that a section on the forum for recommendations or "to be avoided" would be of great help for those who are considering having a barrel threaded.
Best,
George