[Scorch]

kraig-
The idea of a brake is to vent gases to reduce the so-called "jet effect" or "rocket effect" that occurs as the expanding propellant gases hit the stationary atmosphere. You can get as fancy or as rudimentary as you want. A brake needs one or more expansion chambers, a barrier to deflect the gases (bored slightly over bullet diameter so the bullet can pass through safely), and ports (90 degrees to the bore for maximum effectiveness, angled forward reduces brake effect but reduces noise, angled back does not increase brake effectiveness but increases noise substantially).

The brake does not need to be harder than the barrel, the reason many brakes are harder than the barrel is they are cast or forged. As far as what to material to use, there are options. I use pieces of old barrels, they are on hand, they are relatively soft and machine well, and I know they will handle the pressure.
* I bore to .030" over the bore diameter of the rifle it will be installed on, cut two or three expansion chambers separated by .100", and port by drilling into the expansion chamber. You can put as many ports as you want in any pattern you want. Turn to desired outside diameter or profile. Bore and thread one end to screw onto the muzzle. Turn and thread the muzzle for the same thread you did the brake, and screw it on.
* Or using the shank of an old barrel, bore .030" over bore diameter, cut two expansion chambers inside .250" wide separated by .100", and drill completely through the brake chambers at 90 degrees to the bore using a 1/4" (.250") drill. Turn the brake to whatever profile you like. Then bore and thread the brake, and turn and thread the barrel. You will need to index the brake so the ports are on the sides. This will give you a very good brake that looks something like an artillery brake.
* If you are good with a boring bar, you can make integral brakes pretty easily. They look good and impress the heck out of gun nuts, but you run the risk of having to cut back the barrel if you mess up. Counterbore the muzzle .030" over bore diameter for .600", cut three reliefs .100" wide X .100" deep spaced .100" for expansion chambers, then put the barrel in an indexing head and drill multiple ports into the expansion chambers with a 3/32" (.094") drill. I started doing this in 1985, and in 1990 Savage started offering barrels with integral brakes on some rifles. I should have patented it.

If any of this makes no sense, just PM me. I'm better at doing it than explaining it.