I was sitting around with Kevin Brittingham and Reed Knight talking about gun stuff and one of the things they agreed on was a mutual annoyance at how people don’t use the right word to describe the thing on the end of their muzzle. Heck, even some gun guys don’t really know the difference. So, at their request, I figured I would write a quick article trying to explain the difference between the three main muzzle devices in use today . . .
When you buy an AR-15, or any modern rifle with a threaded barrel, the default muzzle device is a flash hider. It’s the standard issue muzzle device for the M16 and M4 rifles in the U.S. military, and since the current service rifle is the model for civilian firearms that’s what the gun companies use by default as well.
The idea behind a flash hider is pretty simple to understand. When a gun fires, especially a gun like the AR-15, most of the powder is burned inside the barrel and used to propel the projectile downrange. However, snce the 5.56 NATO cartridge was designed to completely burn in a 20 inch barrel, there’s 4 missing inches that leads to some unburnt powder being left over after the projectile is long gone. That unburnt powder combusts as soon as it clears the end of the barrel, resulting in a large fireball that is very visible — especially on the battlefield. Even for civilian shooters, that fireball has a tendency to obscure the sights and make follow-up shots hard to make.
A flash hider works by efficiently mixing the air and the unburnt powder at the end of the muzzle in such a way that there is no flash. To understand exactly how it does that requires a mixture of fluid dynamics and chemistry, a background that I lack. But you can see that it works by comparing a gun with a flash hider with one that only has a bare muzzle.
There are different kinds of flash hiders, and the most efficient are the three pronged variety. Whether manufactured by Knights Armament or Vortex or AAC, they all efficiently make that flash disappear. The birdcage flash hider that is used on most AR-15 rifles is also pretty efficient, but the real reason why it’s used is that it’s a combination flash hider and compensator.
A compensator or “comp” is a muzzle device designed to counter the vertical movement of the barrel. The body mechanics involved in firing a gun means that there’s a good bit of “muzzle flip” when the gun goes off, an effect where the recoil of the gun is translated into the muzzle climbing vertically. In order to counter that effect, a compensator vents some of the gasses from the barrel vertically. As we remember from physics every action has an equal but opposite reaction, so the gasses have the effect of forcing that muzzle back down on target.
The A2 birdcage flash hider (on the M16 / AR-15 rifle) has cuts on the top of the device that vent the gas and look like a bird cage, but the bottom of the device is solid. Not only does this keep the muzzle blast from kicking up much dust, but also provides a surface against which the gasses can push to force the muzzle back down.
Compensators and flash hiders are great, but they don’t do a damn thing to mitigate the felt recoil of the firearm. Something hard hitting like a .50 BMG rifle has a ton of recoil that, if not properly mitigated, can do some serious damage to your body. That’s where the brake comes into play.
A brake is designed to take some of the kick out of the gun. As the bullet leaves the muzzle of the gun, the expanding gasses that follow quickly start escaping along the path of least resistance — which usually means slightly to the side and around the bullet. With a muzzle brake, those gasses first hit a solid metal wall before being vented out the sides. Once again the wonders of physics take over, and the pushing forward on that metal wall move the gun forward and counteract some of the rearward force of the gun.
While a brake can vent those gasses in any direction, most brakes vent the gasses straight to either side of the barrel and not vertically into the line of sight of the shooter. It also creates a pressure wave that moves horizontally along the firing line, often annoying those to the side of the shooter.
Another increasingly popular form of muzzle brake is the silencer. The baffles in the can that slow the gasses and turn that loud “BANG” into a more squishy noise also act like a massive muzzle brake and greatly reduce the recoil of the gun. That’s one of the reasons that a Neilsen device is required on a handgun silencer, a spring or piston that allows the barrel to recoil enough to kick the slide back and cycle the action as the silencer itself is being moved forward by the gasses.
Naturally, the ideal muzzle device combines one or more of the features of the devices above. That’s why combination devices, like the A2 flash hider, are extremely popular. The most common muzzle device for competition shooters is the compensating muzzle brake, which reduces vertical muzzle climb and felt recoil without caring about the visibility of the firearm. As a result, some fantastic muzzle flashes can be seen in the chambers of the device as the gun goes off.
The ideal muzzle device, by any account, is a silencer. It reduces all of the above (well, after the first shot for muzzle flash) and does it extremely efficiently. That’s one of the reasons that muzzle devices come under heavy scrutiny in competition shooting since a bigger muzzle device can give a shooter an unfair advantage.
Personally, if I can’t have a silencer, I prefer a straight muzzle brake. Vertical climb is something I can handle with sufficient training, but any little bit of help I can get in the recoil department is always appreciated.