We strongly recommend a standard 5/8-24 thread; however, we can do any thread pitch. There needs to be enough thread section, a thread relief cut, and a sufficient shoulder behind the threads. Everything has to be square and true and the threads need to be in spec. Most of our customer problems with tight threads come from non-standard thread patterns that were cut for a proprietary brake. They are typically either not cut to spec at all (ie just matched to the brake), or they are on the very tight end, which leads to problems. Your gunsmith should thread to class 3 thread specs and should use gages to determine thread fit -- not the suppressor!