I have several rifles with muzzle brakes installed and they WORK and work well IF you get the right ones, they are not all equal!!!!
I have the Hi-Tech brakes which are made from scratch for the individual rifle. The tolerances are tight and this why they work so well. If a brake is made properly it will vent of, at a 90 degree angle, most of the gases produced by the powder burning. These gases are traveling between 5000 and 6000 FPS when they leave the muzzle so it takes the 'sharp' (high velocity) recoil away and the rifle will 'push' you similar to the way a shotguns does.