So my brother bought a muzzle brake for his .300wm but die to its incredibly thin barrel (Winchester model 70 shadow, it's .575" thick at the muzzle) at the recommendation of the vendor he bought it from he bought a 1/2" threaded muzzle brake. Now, that leaves .134" of barrel wall between the groove And the... Atmosphere. At the behest of a local gunsmith we didn't thread it, and it looks like we might be sunk on the idea of a brake for this rifle. I was told that a general rule of thumb for muzzle threading is .5" for .223, 9/16 for 6.5 or .270, and 5/8 for .308. This all holds true I imagine? Thanks fellas.