Muzzle brake

The muzzle brake of the 105mm gun on an AMX 10 RC fighting vehicle.

Muzzle brake of the Sig 550 rifle

The S&W Model 500 features a muzzle brake.

A muzzle brake or compensator is a device that is 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. On the AKM assault rifle, the brake is angled slightly to the right to counteract the sideways movement of the gun under recoil.

Concept

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 gasses 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 gasses rather than redirection. Slowing of the gasses is the method used on Suppressors and linear compensators. In conventional designs, combustion gasses 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 gasses is significant enough to move the firearm in the opposite direction of recoil.

Utility

There are advantages and disadvantages to muzzle brakes. Recoil is a subjective concept. One shooter may precieve 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 even if the same total energy is transfered. Though there are numerous ways of measuring the energy of a recoil impulse, it's generally true that between 10% and 50% reductions can be measured. One of the primary advantages of a muzzle brake is the reduction of muzzle rise. This allows a weapons sights to be realigned quicker. This is relevant particularly for fully automatic weapons. Muzzle rise is often reduced 100% by an efficient design. Because the rifle moves rearward less, the shooter has little to compensate for. This is particularly true of rapid-fire, fully-automatic fire, and large-bore hunting rifles.

The disadvantages of a muzzle brake are many. Escaping gas creates four effects: noise, pressure, blast, and flash. Noise increase is necessary to most designs because higher velocity gassses impart more energy to counteract recoil. Higher velocity produces greater noise. Pressure is felt as a shock wave similar to that made by an explosion. The blast is the physical movement of air. This has the effect of blowing up dust and debris from below and to the sides of the brake. Finally, flash is increased as the high pressure gasses mix slowly with surrounding air, staying hot enough to glow for a longer period of time.

Muzzle brakes on both small arms and artillery can cause escaping gases to throw up dust clouds, impairing the firer's visibility and revealing his position to the enemy. Troops often wet the ground in front of antitank guns in defensive emplacements to prevent this.