If memory serves me correctly, I'm using 1/2 x 28. It sounds like you need a different gunsmith......Justin,
What thread diameter is that? I bought a 1/2 x 28, sent it to a smith with my barreled action and he would not thread it. There was not enough material on the barrel. Additionally, if i jumped to the 9/16 variety, I was told there would not be enough "shoulder" for the brake to seat against.
Can you recommend a Smith to thread my 7mag T3? I'm having a helluva time finding someone to do it for me. I called APA and left a message but have not heard back from them.
Matt Whaley in Idaho did my last one, and Al Seaman has done a bunch for me. Both do very good brakes.