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Gunsmithing AR-15 For the Love of Competition Rifles

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

by Joseph von Benedikt   |  August 29th, 2013 15

Photo by Tim Yan

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.

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.

  • Andres Hernandez

    “but have little affect on recoil” No big deal, just and FYI asking you to read proof before publishing

  • Rob

    If you need a muzzle break on an AR, I suggest you put down the big boy guns and get yourself a Red Rider instead. The only thing you do when you put a break on an AR is PISS OFF the people next to you at the range. Put a damn flash hider on it.

    • Trident731

      Rob, I think you missed a couple of paragraphs. I suggest a second reading. Muzzle brakes are quite popular in my state as well, the Legislature doesn’t trust it’s Citizens with threaded barrels and flash hiders. I suppose that’s my tough luck, however I don’t think the money that I could save paying my NRA dues could cover a move. Thanks to the author for this article!

      • Rob

        It sucks that some states ban features like that because they are scary. I guess in your position you have no choice. I live in a state where they are legal. The only reason I hate them is because of the concussion from the bench adjacent to me. My little girl had to walk away from the bench a few weeks ago because it was hurting her head every time the guy next to her fired. I could hardly focus on her shooting, and since we had a close call with a squib recently, I’m trying to make sure every shot clears the barrel.

        I understand the article completely. I can’t understand why anyone needs a brake on an AR though, aside from full auto or 3 round burst. Not like they have any recoil. I’ll stick with my original theory that nothing less than a .338 should have a muzzle brake.

        • Orville Thomas

          Nothing I see in the article indicates anyone HAS to or NEEDS to put a muzzle break on a AR. The article provides information about muzzle breaks and how they operate.

    • Rob

      Your momma

  • Facts nothing but the facts

    Flash Hiders are Illegal in my state , the people at the range could care less how loud your gun is

    • Greg

      I guess you don’t really shoot, or you are already deaf. People do care about noise, at least people I shoot with do. 2-3 shots from my 50 cal without letting people know you are about to shoot and you get some really nasty looks and comments. Some guns are just painfully noisy.

  • Ian

    I have a Jerry Miculek muzzle brake on my ar-15. I purchased it because I wanted something else besides the standard, boring, bird cage muzzle! I am happy with this brake, and most importantly, it looks cool. As for the question of do we really need a brake on an ar-15, probably not, but hey, it’s my rifle, not yours. I do have bigger guns with no brakes on them, so don’t tell me to go shoot a Red Ryder! Maybe you need better ear protection. You know, it is a gun range! My seven year old doesn’t mind my K98 Mauser.

    • John T.

      Well, as long as it looks “cool”….

      Hearing protection doesn’t stop muzzle-blast, which is what most people have a problem with. They may complain about the noise, but it is the blast that is really hard to tolerate. The blast has a significant effect on those that are situated to the sides of the break, where the gasses are directed. Muzzle-blast can damage hearing and can also lead to headaches nausea. Even on an open range, while standing above a shooter firing from the prone with an M4 (14.5-inch barrel), I would tend to develop mild headaches after a several firing orders. Even the ‘little’ 5.56 has enough blast to be mildly annoying.

      Your K-98 doesn’t have a break on it, does it? Probably not. As an experiment, thread the end of the barrel and install a side-venting muzzle-break. Now, place your 7-year-old kid, 90-degrees to the muzzle, about 3-feet away, wearing both ear plugs and muffs. See how long your kid stands there.

      The shooter, because he is behind the rifle, doesn’t notice how brutal the blast is, since it is directed to his sides. Anyone standing near the muzzle is pummeled. Many guides will require you to remove a break from your rifle while on a hunt, for that reason.

      You are free to put whatever type of device at the end of you barrel that you choose, but understand that your choice affects others around you.

      Many of the ranges I used to shoot at are semi-enclosed. Often, on a crowded range, idiots would show-up with super-magnums with muzzle-breaks threaded on the ends of their barrels. Upon firing, the blast would be so severe that paint chips would be blown off the roof over-head and dust would go flying everywhere. Those people visiting the range, simply trying to enjoy a little target shooting, would pack up and leave. When complaints were made to the shooter, often the response would be that they have a ‘right’ to shoot with a muzzle-break, if they want to. Great ambassadors to the shooting sports. A simple solution is to remove the break, but that would ruin their ‘fun’.

      Some guns are a lot more manageable with muzzle-breaks, no doubt. Breaks have their place, and there is nothing wrong with them under certain conditions. The typical AR type carbine with a bird-cage flash hider is tolerable, even on an semi-enclosed range. However, people’s tolerance for muzzle-blast varies. Break design also matters. The more gasses vented to the sides, the more blast directed at your fellow shooters. The typical AR may be okay, but bump up the power factor, or shorten the barrel, and muzzle-blast goes up significantly.

      I say all of this not as a attack on muzzle-breaks, but as a little food for thought, for those that use them on their rifles. Nobody is telling you that you shouldn’t use one, but only that you consider those around you on the firing line. Getting the snot pounded out of you by the blast from somebodies .300 super-stupid-short-fat-dumb-ass-magnum does not make for an enjoyable outing to the range, nor doesn’t it spread good will to your fellow shooters.

      • 8inch54 at the mini-golf

        Egad. Er … Egad

  • aero

    A company called wellington arms makes shielded muzzle brakes which force the noise and the flash forwards instead of sideways. You can check them out at

    • Brandon

      Troy makes one called the “Troy Claymore” that does the exact same as the one you mentioned for $55-$60

  • Regina Pecoraro

    Has anyone tried a BattleComp?
    They seem to be a bit high in price but I want something that will last with a few rounds down range…. Plus my state places too many restrictions on me

  • brad

    They’re guns they’re loud. Get over it. Or maybe just stay home.

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