Re: crown for muzzle break
I think the best crown under a brake is no crown. Just single point the muzzle at 90 deg from the bore out, and don't cut a recess at all. You will either have to always have the brake on (or a nut) to protect the muzzle though. Seems like some brakes want to have the muzzle flush with the back wall of the first chamber, or some want the muzzle slightly in front of the back wall. Either way, it would seem that a perfectly square muzzle would be the most consistent under a brake.
There are 2 advantages to the 11 deg crown as JE described. First, you would always have a protected muzzle even with the brake off. Second, it makes sense that the slightly obtuse (101 deg) angle makes the edge of the bore resist hot gas and cleaning brush erosion better. You could accomplish the same (or better) bore edge protection by cutting a small chamfer, like factory barrels. I don't do it because I think the perpindicular cut is the most precise cut you can make, and a chamfer isn't.
I've seen all kinds of crowns on rifles that were extremely accurate, including some with a chamfer cut on them, so this is all just my opinion. Probably any kind of crown that is concentric and true to the bore edge is fine, but to me, the addition of a brake makes it a little more tricky.
Good hunting, Tom
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time