A muzzle brake or recoil compensator is a device attached to the muzzle of a firearm or cannon that redirects propellant gases to counter recoil and unwanted rising of the barrel during rapid fire.
They have been used in various forms for centuries. Early forms were intended simply to reduce bruising when firing large cannons. Modern muzzle brakes are very effective at reducing recoil and are sometimes used in lieu of a buttstock damping device. The majority of muzzle brakes are screwed onto the muzzle of the gun, but some guns have muzzle brakes that are integral to the design of the barrel.
Muzzle brakes are simple in concept: they allow some of the high-pressure gas from the burning powder to be diverted sideways and rearward instead of all back into the breach. This redirection causes the muzzle to rise less, which in turn reduces recoil. This can be a great benefit for shooters who are recoil sensitive, or who simply want to minimize the amount of movement their gun makes when firing. Muzzle brakes can also help to increase the accuracy of rapid-fire, as there is less muzzle rise to throw off the aim.
The pressure reductions can be dramatic, slashing nominal felt recoil by as much as 95 percent. But there are secondary consequences to muzzle brakes. One is that they tend to be very loud–sometimes dangerously so, especially to the shooter’s ears if not wearing hearing protection. Muzzle brakes also increase the flash signature of a firearm, and can redirect hot gases and debris toward the shooter and others nearby.
The principle of its operation is illustrated here: