From Wikipedia, the free encyclopedia

It has been suggested that Ported barrel be merged into this article or section. (Discuss)

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

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^[1]. 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^[2].

A muzzle brake is external to the barrel of the firearm or cannon, while a recoil compensator is typically part of the structure of the barrel proper.

Prominent muzzle brake of the PGM Hecate II.

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^[3]. 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, 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^[4].

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^[2].

The S&W Model 500 features a muzzle brake.

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 even if the same total energy is transferred. 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 weapon's sights to be realigned more quickly. This is relevant particularly for fully automatic weapons. Muzzle rise is often entirely eliminated 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. They are also common on small-bore varmint rifles, where reducing the muzzle rise allows the shooter to see the bullet impact through the scope.

The advantages of brakes and compensators are not without cost, however. The most obvious of these to the shooter is the increase in the perceived muzzle blast. The sound and flash normally projected largely away from the shooter are now directed outwards or even backwards towards the shooter. Eye and ear protection for the shooter and nearby spectators are even more essential when a brake or compensator is used.

Linear compensators and suppressors do not have the disadvantages of a redirected muzzle blast, because they actually reduce the blast, and vent forwards. The downside to these is that to be effective, they must have the volume to contain a significant amount of the powder gas, so they can hold it while it is allowed to slowly vent. This can add significant bulk to firearms with large propellant gas volumes.

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. Troops often wet the ground in front of antitank guns in defensive emplacements to prevent this, and snipers are specially trained in techniques for suppressing or concealing the magnified effects of lateral muzzle blast when firing rifles with such brakes, such as the M82 Barrett rifle.

Flash suppressor of the Sig 550 rifle. Flash suppressors are often designed to work as simple muzzle brakes.

Muzzle brakes were ruled "legal" by the ATF in the United States a short time after the now defunct Federal assault weapons ban went into effect in 1994. These muzzle attachments were legal to attach to a threaded barrel, so long as it was welded in place on certain firearms (silver solder also suffices). On the other hand, flash suppressors, and barrel shrouds were seen as 'military' features, and were on the list of features that, provided enough features were also present on the semi-automatic rifle, then the rifle was defined as illegal, if manufactured after the effective date of the ban. This meant, in practice, muzzle brakes had to be certified by the ATF to prevent end-users from accidentally violating the law and installing a device that could later be found to be defined legally as being more of a flash suppressor than a muzzle brake, even if marketed and sold as a muzzle brake, if incidental flash suppression was deemed to be 'significant' by the ATF. The Federal laws governing this sunsetted in 2004, and are no longer of active concern, except in those few jurisdictions in which certain provisions are still retained in specific state laws.

• Muzzle booster

1. ^ Muzzle brake in the NRA Firearms Glossary
2. ^ ^{a b} STI article on Limcat Undergas Bypass Turbo System recoil compensator
3. ^ LeVang linear compensator
4. ^ Mag-Na-Port handgun porting information

• Chuck Hawks' article on muzzle brakes