Barrel vise blocks and a quality wrench, I think its either 5/8s or 1/2" I forget exactly what size but one of the standard imperial wrenches fits fine. I had a factory LMT one that took and extreme amount of force to remove. I couldnt have done it without the barrel in the supporting vise blocks. Some others seem to almost get them off by hand. You can get the barrel vise blocks cheap at Brownells. They are a worthwhile investment if this is something you will do occasionally, like trying different muzzle brakes and stuff.