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G&A Basics: How AR-15 Muzzle Brakes Work

Contrary to popular opinion, the way muzzle brakes work is less voodoo magic than it is rocket science.

It's true, so you can leave the incense at Auntie Mildred's cottage when you head to the range to mount and tune an AR-15 muzzle brake. All you need is a wrench and a basic understanding of how a brake works in order to get the best out of it.

How Muzzle Brakes Work


Like the rocket drawings you saw on 7-Eleven comic book racks back in the day, muzzle brakes — also known as compensators — harness exploding gunpowder gases and "ejecta" — particles, burning and otherwise — and redirect them in order to change the acceleration, or movement, of the rifle. Baffles inside the brake create an expansion chamber, and holes drilled into that expansion chamber bleed gas off at various angles to the axis of the barrel. These gases provide jet-like force immediately before, during and after the projectile actually exits the barrel, resulting in effective muzzle redirection.


A close look at the brake/barrel interface and the brake's internal guts reveal that as a bullet exits the rifled portion and crown — the last point the projectile touches as it heads downrange — it enters a slightly oversized tunnel through the brake. It must be oversized to allow the bullet free passage — if the bullet touches the inside of the brake with even the pressure of a whisker, it will be thrown off and become inaccurate.

Hot gases boil into the muzzle brake the instant the bullet's base exits the barrel, expanding violently and traveling at several times the speed of the projectile itself. Blowing forward around the sides of the bullet and following it, the gases hit baffle after baffle and jet hole after jet hole, expanding into the expansion chambers and being redirected out the sides of the brake.

Where and how those jet holes are placed in the muzzle brake has a tremendous effect on the influence of the brake in terms of recoil and muzzle movement (direction). If the holes are drilled at a 90-degree angle to the surface of the brake, the force the exiting gas applies is different than if the holes are drilled with a slight angle forward or rearward. If the holes are drilled in equal spacing all the way around the brake, applied force works only to reduce recoil, not direct or eliminate muzzle movement.

To reduce muzzle movement — typically termed "muzzle jump" — the holes must be drilled in the top and sides of the brake, but not the bottom; taking it a step further, the holes must favor one side or the other to counteract the effect of rifling spin direction on muzzle jump. Believe it or not, rifling direction does have a rather significant effect on directional recoil.


Using a crescent wrench, you can tune your brake's effectiveness by turning it a bit at a time until you find that sweet spot. Generally, most modern barrels use a right-hand rifling twist, so the top gas ports should be slightly to the right of perfect top center.

Why We Use Them

Very rudimentary brakes — such as the slanted cut seen on the muzzle of many AK-47s — have no baffles or even gas ports. Instead, they just give the exiting gases a general shove in a direction favorable to reducing recoil and muzzle jump. Have you ever wondered why the angled cut on those AK-47s isn't oriented straight up? It's because turning it just past center or just short of center — depending on the direction of the rifling twist — helps keep the AK from jumping straight up by counteracting the effect of the rifling twist.


The most sophisticated, aggressive muzzle brakes generally incorporate both expansion chambers and gas ports, and sometimes very large, rearward-angled gas ports into their design. Often there are two or three massive gas ports on each side, and several smaller gas holes on the top. They are extremely effective — and obscenely loud — and are favored for very hard-recoiling rifles, or to completely eliminate the affect of recoil on competition rifles such as AR-15s. And yes, they are often set at a slight angle to counteract the rifling.

Brakes that have gas ports but no baffles or expansion chambers are popular for bolt-action precision rifles and big game rifles. Generally much smaller in diameter and featuring gas holes 360-degrees around the brake, they are somewhat less effective, but much quieter than more sophisticated, aggressive brakes.

Muzzle Brakes vs. Flash Suppressors

Before choosing a muzzle device, it's important to consider the primary purpose of your AR-15. If the purpose is self-defense, you'd be better served with a flash suppressor than a brake.

What's the difference? Muzzle brakes tame recoil and muzzle jump but are tremendously loud and usually spit a pretty good fireball. Flash suppressors, however, tame the flash generated when unburned or burning gunpowder particles and gases contact oxygen, but have little affect on recoil.

Flash suppressors are also much quieter than muzzle brakes, making them far more suitable for personal protection use, especially indoors where loud guns cause significant hearing loss. If nighttime or low-light shooting is probable, a flash suppressor will protect your night vision, but the flash of a muzzle brake will momentarily destroy it. In some scenarios, that alone could mean the difference between living and dying.

On the other hand, if you are competing in 3-gun events with your AR-15, the recoil dampening qualities of a brake can enhance your speed, and a properly tuned brake will eliminate muzzle jump entirely, keeping your sight in the same place through recoil. Double-tapping a target can be done quickly with a good brake installed.

Predator hunters and varmint shooters can also benefit from a good muzzle brake because eliminating muzzle jump enables the shooter to spot his or her own impact through a riflescope.

Hybrids

There are some crossover muzzle devices. While they aren't as effective at dampening recoil as a proper muzzle brake, or as effective at killing muzzle flash as a proper flash suppressor, they're worth considering if you want a bit of both worlds. The one I have the most experience with is basically a modified A2 military-type flash suppressor with no gas cuts on the bottom portion of the device. As a result, escaping gases are directed upward, reducing muzzle jump in a small way, and at the same time, flash is partially reduced.

There are a lot of good muzzle devices. However, I can't come right out and tell you that "X" brake by "Y" manufacturer is the best. Brake effectiveness depends on many things: body type, height, stance, hold, ammunition type and so much more. The only right way to pick the perfect brake for you is through trial and error.

Personally, I'm a performance kind of shooter. On an AR-15, I like more aggressive muzzle brakes and suppressive flash suppressors. Flash suppressors are a topic for another time, but for now, here's a list of 10 popular muzzle brakes to tame the recoil on your AR-15.

JP Enterprises Bennie Cooley Compensator

Recoil Control: Aggressive
Dust Signature: Low
Price: $90

Available in both stainless and black oxide finish, the JP Enterprises Bennie Cooley Comp was the first super-effective brake I ever used many years ago. It's shockingly good at reducing recoil — rated to eliminate up to 70 percent — and has top ports to reduce muzzle jump. It's sized to be legal in competitive tactical disciplines.

Primary Weapons Systems FSC

Recoil Control: Moderate
Dust Signature: Medium
Price: $99

Designed for entry and breaching teams, the Primary Weapons Systems FSC directs most gasses forward to reduce blast and noise. It also features a flash-suppression element incorporated into the front to reduce flash and direct what little remains away from the shooters line of sight. Includes a peel washer for easy indexing of the ports.

Smith Enterprises Good Iron

Recoil Control: Aggressive
Dust Signature: Low
Price: $89

The Smith Enterprises Good Iron is constructed of the same high-grade 8620 bar stock steel as my favorite flash suppressor, the Smith Vortex. With rounded, non-snag edges, top-shelf engineering against muzzle jump, and easy-to-install design; it's an excellent choice for shooters wanting a very aggressive brake.

Surefire Muzzle Brake/Suppressor Adapter

Recoil Control: Aggressive
Dust Signature: Low
Price: $149

Constructed of heat-treated stainless steel, the Surefire Muzzle Brake Adapter offers high corrosion/erosion resistance, highly effective recoil compensation and serves as a mount for a Surefire sound suppressor if desired. Touted to minimize point of impact shift with/without sound-suppressor use, it is also said to minimize the concussion felt by the shooter while firing.

Advanced Armament Brakeout Compensator

Recoil Control: Moderate
Dust Signature: Moderate
Price: $99

Finished in ultra-durable, erosion-resistant SCARmor — a trademarked finish — the Advanced Armament Brakeout Compensator is a dual-duty compensator and flash suppressor. As with any performance device, a combo-purpose unit will never be as effective a brake as is a dedicated compensator, but it does offer versatility. Built beefy to withstand extreme use and abuse, it also serves as a mount for AA sound suppressors.

Battlecomp Compensator

Recoil Control: Aggressive
Dust Signature: Low
Price: $149

Of rather non-traditional design and appearance, the Battlecomp Compensator allegedly reduces flash signature and the concussion felt by the shooter. A version pre-drilled for permanent pinning to 14.5-inch barrels — to make a civilian-legal 16.1-inch barrel — is also available.

Benny Hill Rolling Thunder Compensator

Recoil Control: Aggressive
Dust Signature: Low
Price: $99

The Benny Hill Rolling Thunder Compensator is made of stainless steel and features a single, carefully engineered, top gas port with its own expansion chamber to reduce muzzle jump, and three large ports on each side to dramatically reduce recoil. It's aggressive and effective, enabling shooters to stay on target through very fast rapid-fire strings.

DPMS Levang Linear Compensator

Recoil Control: Moderate
Dust Signature: Moderate
Price: $39

The concept behind the DPMS Levang Linear Compensator is simple: Too much noise is not a good trade-off for reducing recoil. The Levang Linear Comp directs all gas forward, away from the shooter, and is allegedly very quiet for a compensator. It may not tame recoil completely, but it's a lot easier on your ears.

DPMS Miculek Compensator

Recoil Control: Aggressive
Dust Signature: Low
Price: $49

The DPMS Miculek Compensator is both simple and effective, making it an inexpensive muzzle device that is aggressive and very easy to clean. It has side ports only, so it does not specifically address muzzle jump. Shooters with handyman skills and a drill can add a port or two on top if they feel it's needed, but most are pretty happy without.

Precision Armament M4-72 Severe-Duty

Recoil Control: Aggressive
Dust Signature: Low
Price: $79

Beautifully machined, the Precision Armament M4-72 Severe-Duty Brake is one of the sexiest brakes available. And hey, it's incredibly effective too! As a nice side benefit, it's engineered to reduce gas disturbance on the projectile as it exits, helping glean the best accuracy possible.

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