Muzzle brakes and recoil compensators are devices that are fitted to the muzzle of a firearm or cannon to redirect propellant gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire. Muzzle brakes are very useful for combat and timed competition shooting, and are commonly found on rifles firing very large cartridges (often big-game rifles), as well as some artillery and tank guns. They are also commonly used on pistols for practical pistol competitions, and are usually called compensators in this context.
Muzzle brakes are simple in concept. One of the simplest designs can be found on U.S. 90 mm tank guns. This consists of a small length of tubing mounted at right angles to the end of the barrel. Brakes most often utilize slots, vents, holes, baffles, and similar devices to redirect and control the burst of combustion gases that follows the departure of a projectile. Another method, called porting involves ports or holes in the barrel near the muzzle that vent gas prior to the departure of the bullet. A third method involves slowing the departure of combustion gases rather than redirection. Slowing of the gases is the method used on suppressors and linear compensators. In conventional designs, combustion gases depart the brake at an angle to the bore. This counteracts the rearward movement of the barrel due to recoil as well as the upward rise of the muzzle. The effect can be compared to reverse thrust systems on aircraft jet engines. The mass and velocity of the gases is significant enough to move the firearm in the opposite direction of recoil. On the AKM assault rifle, the brake is angled slightly to the right to counteract the sideways movement of the gun under recoil.
Construction of a brake or compensator can be very simple; the AK-47, for example, some models used a diagonal cut at the muzzle end of the barrel to direct some of the escaping gases upwards. Another simple method is porting, where holes or slots are machined in the barrel near the muzzle to allow the gas to escape.
More advanced designs use baffles and expansion chambers to slow down the escaping gases; this is the basic principle behind a linear compensator. Ports are often added to the expansion chambers, producing the long, multi-chambered recoil compesators often seen on IPSC raceguns.
There are advantages and disadvantages to muzzle brakes. Recoil is a subjective concept. One shooter may perceive it as pain, another as movement of the sights, and another as rearward thrust. Recoil energy can be sharp if the impulse is fast or may be considered soft if the impulse is slower, even if the same total energy is transferred.