I decided I wanted more thread. I took off the brake, and used a small clamp as a collar to keep the file or grinder from going too far up the barrel. I made an area wide enough to give slightly more than 1/2" threaded area, instead of the 1/4" I had. The clamp is a trick I used for cutting a straight line around Saiga barrel shrouds.

I clamped it on, and started with a flat file to start reducing from .562" to .5". You do half the barrel (the clamp screw assembly prevents you from doing all the way around), then rotate the clamp 180 degrees and do the other side. After starting with the flat file, I transition to a round Dremel stone, then switched to a sanding drum with a 1/2" drum. I used a 1/2" shaft collar as a gauge. The hose clamp gave me a perfect symmetrical shoulder.

One it was 1/2". I resumed threading. I ended up with slightly more than 1/2" as desired. No worry now about the 50,000 PSI shock wave pushing the muzzle brake off.