Have a gunsmith turn down and thread the end of your barrel to 5/8" x 24t, which is the standard for commercial production brakes.
This is all easy to do as part of the build, before he fits the barrel to the action. Depending on what you select he can machine/contour the brake to your barrel OD for a seamless transition.
Here's one with a .85, very close to the .875 you probably will end up with as a standard Bull contour:
http://www.brownells.com/rifle-part...70.aspx?avs|Manufacturer_1=precision armament