Do You Really Need That Compensator?

Compensators and Muzzle Brakes

Everybody’s seen pistols and rifles with bulbous objects hanging off their muzzles. The most commonly used are suppressors that reduce the noise of a gunshot. They never work as well as they do in Hollywood. For one thing, when a bullet is supersonic, suppressors don’t eliminate the sonic crack of the bullet breaking the sound barrier. Even so, they have their uses, in particular saving the shooter’s hearing.

More recently, other devices have started showing up on pistols and rifles. John Wick likes an H&K P-30L. Already a large pistol, it looks bigger with a compensator stuck on the end. With the imprimatur of Keanu Reeves, there is an undeniable cool factor. Picatinny rail, all sorts of vents. But what does it do?

In this article, we’ll take a quick look at compensators and muzzle brakes. Talk about what they are for, how they work, and some of the issues they introduce that a shooter might not be aware of.

Recoil and Muzzle Flip

It’s Newton’s third Law of physics: for every action, there is an equal and opposite reaction. When a bullet leaves the muzzle of a rifle with a certain amount of force, the rifle slams back into your shoulder. There are nuances. You feel more recoil with a bolt-action rifle than you feel when you fire an AR. Why? Some of the energy of the weapon’s discharge is used to cycle the action. When you fire a revolver, all the shock of recoil goes into the weapon’s frame and into your hand. When you fire a 1911, some of the recoil goes into blowing back the slide to eject the spent casing and chamber the next round.

You feel the shock of recoil, and the muzzle of your weapon jerks upward. A portion of the force goes back into your arm and shoulder. Another portion of the force flips up the muzzle. That muzzle flip slows you down. You can lose your sight picture and have to reacquire it.

The purpose of a compensator is to redirect the explosive gases of the gunshot upwards to counteract the muzzle flip. Compensators are very simple devices, and they’ve been around for a long time.

Look at Figure 1. The compensator has vents along the top. That directs some of the expanding gases upwards as they leave the muzzle. Newton’s third law pushes the muzzle back down. Look at a Thompson submachine gun of World War II vintage – Figure 2.

Now, we can see why one would want a compensator on a fully automatic weapon. They’re notorious for muzzle climb. That’s why experienced shooters don’t fire long fully automatic bursts unless they can control the weapon. Firing a short burst allows the shooter time to bring the muzzle back down. A compensator can help improve the weapon’s controllability on full automatic.

Muzzle Brakes

Figure 3 shows an image of a muzzle brake.

That’s a World War II Tiger tank with an 88mm gun. When it fires, you can actually see the barrel recoiling straight back into the sleeve. Crew inside the tank can be maimed or killed if they sit in the wrong place. The purpose of the muzzle brake is to moderate the weapon’s recoil. It does that by redirecting some of the gases as they leave the barrel. It directs a portion of the muzzle blast backwards. Newton’s third law. The gases directed backwards project a certain amount of force forward, reducing the recoil.

You frequently see muzzle brakes on heavy-caliber rifles like the one shown in Figure 4. This one actually looks like a combination of muzzle brake and compensator.

Why do I say it looks like a combination? Look at Figure 1 and Figure 2. The vents on compensators lie along the top of the device. The vents on muzzle brakes usually lie along the sides. The position of the vents reflects their purpose. The dorsal vents of compensators direct muzzle blast upwards to fight muzzle flip. The lateral vents of muzzle brakes direct muzzle blast to the sides and backwards. More telling, the bottom of the device looks flat. The vents look designed to direct muzzle blast backwards, sideways, and up. But not down.

There’s a bipod on that rifle. If you’re firing prone, you do not want your muzzle brake to direct muzzle blast downward and kick up a whole lot of grit and dust in your face. Look at Figure 4. The vents are lateral, but angle upwards ever-so-slightly.

It’s not that simple.

It should be clear that any time you hang something extra off the muzzle of your weapon, you are going to alter its balance and concealability. There are some very small compensators available now. The so-called minis. But not all the effects of compensators and muzzle brakes have to do with size and balance. Some are subtle.

Compensators, muzzle brakes, and suppressors can alter your zero and point-of-impact. If you’re not aware of these effects, your experience with these devices will be frustrating.

I’ll briefly introduce two effects here, and get into them in more detail in subsequent posts.

Harmonics

A rifle is a steel bar. So is a pistol, although it is much shorter. Imagine taking a long steel rod in your hand and striking it on one end with a hammer. That rod is going to vibrate. If you study it closely, you’ll find the vibrations follow a standing sine wave that looks like Figure 5.

Those vibrations will result in increased dispersion in your shot group. The nodal points are stable; everywhere else is vibrating. The amplitude (height) of the wave is greatest at a point along the baseline called an antinode. The greater the amplitude at the muzzle of your barrel, the larger the dispersion of your bullets as they head downrange. You get a bigger circular error probable (remember our discussions of artillery and missile accuracy). You want to do things that reduce the amplitude of the wave as the bullet leaves the barrel. As you can see from Figure 5, one thing you can do is use a shorter, thicker barrel. Such a barrel is heavier and more rigid.

That’s why you have rifles sold in heavy-barrel variants.

When you screw on a suppressor or any other device, you alter the harmonics of your weapon. If the device adds weight to the end of the barrel, it can dampen the oscillation at the muzzle. On the other hand, if it’s not screwed on tight, it can create other problems. We’ll discuss these phenomena further another time.

Pull-Off

Compensators and muzzle brakes work the same way. That’s why I decided to treat them together in this introduction.

Think of the firing sequence. Your cartridge goes bang. The expanding gas of the burning gunpowder propels the bullet down the rifle tube. The bullet spins down the tube and exits the muzzle on its way downrange. The expanding gas from the burning powder exits the muzzle behind the bullet. Some of it goes straight forward, producing recoil. A compensator redirects a portion upward. A muzzle brake directs some of it backward, reducing recoil. The compensator and muzzle brake effects occur after the bullet leaves the muzzle (except for the pull-off phenomenon discussed below).

Straightforward. But not quite.

Before you pull the trigger, there is a plug of cold air sitting in the barrel of your rifle. Cold air is denser than hot air – the molecules are packed tighter – so it’s a relatively thick plug.

When you pull the trigger and the expanding gas pushes the bullet down the tube, the bullet compresses that plug of cold air and pushes it along ahead of it. As a result, that cold air leaves the barrel and hits the baffles of your muzzle device before the bullet leaves the barrel. That means there are forces acting on the muzzle of your weapon before the bullet heads downrange. That can alter your point of impact. Under certain circumstances, it might even alter it in an unpredictable way.

Like the harmonics, I’ll discuss further in a later post. For now, you only need to be aware that there are physical forces going on that will affect your shot.

Other Effects

There are a few other things to consider. Suppressors reduce noise; compensators and brakes increase noise. The increase can be significant. Flash suppressors reduce flash; compensators and brakes can increase flash.

Concussion can be an important consideration. A shooter gets behind his rifle, and a muzzle brake directs the muzzle blast backward to either side. Anyone situated at the shooter’s five or seven o’clock might get shaken up. Anecdotally, there are reports of spotters wearing contact lenses that have the lenses squished against their eyeballs. There’s a moment of blurred vision before the lenses pop back.

Conclusion

I can imagine people jumping all over me, but that’s okay. In my opinion, one does not need compensators for small-caliber handguns. I think they could be useful for fully automatic weapons. If you need full auto and want better control of the weapon, it’s an advantage. If you like (and can afford) to do mag dumps with small-caliber semi-automatics, maybe. Compensators may be a good idea for a Desert Eagle.

Rifles are another matter. Muzzle brakes can be a good idea for a heavy-caliber rifle. Something like the .338 or .50 BMG. Below .338, I’m not sure. For 7mm Remington Mag and .300 Win Mag, it’s a personal choice. As we’ve noted above, these are very simple devices, and one can find compensator/brake combinations.

About the Author

You may reach Cameron at: cameron.curtis545@gmail.com

Cameron Curtis has spent thirty years in the financial markets as a trader and risk manager. He was on the trade floor when Saddam’s tanks rolled into Kuwait, when the air wars opened over Baghdad and Belgrade, and when the financial crisis swallowed the world. He’s studied military affairs and warfare all his adult life. His popular Breed series of military adventure thrillers are admired for combining deep expertise with propulsive action. The premises are realistic, the stories adrenaline-fueled and emotionally engaging.

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