What Kevin said. For the most part, there are two types of brakes: Those with evenly spaced ports all around, (axial?), and those with ports out the sides and, some , also the top. The axial brakes do not need to be timed, the others do but often come with shims making this fairly simple. If you are shooting much in the prone position on the ground the axial brakes can cause a lot of dust or dirt to be stirred up...somewhere on the forum is a great write-up on brakes, hopefully someone will post a link. P_102
Do not trifle in the affairs of dragons, for thou art crunchy and taste good with ketchup.