Muzzle Brake VS. Flash Hider
If you are a gun owner, a competition shooter, or even just an occasional shooter, you've probably heard of and seen muzzle brakes and flash hiders on firearms.
Sometimes, when a bullet is fired from a shorter barrel than it was designed for, there is excess powder that is being pushed behind the bullet, so when this excess powder exits the muzzle, it creates a large "flash". Flash hiders were engineered to counteract this problem. Typically seen on military rifles and short barreled military carbine type rifles, flash hiders are simply meant to reduce the amount of flash that exits the barrel following the bullet to prevent the flash from blinding the shooter during low light operations and to reduce flash seen by the enemy.
A muzzle brake acts on the laws of physics and "equal and opposite reaction". It is a device which is typically seen and used on firearms that require recoil and muzzle rise reduction. Examples of these might be the triangular arrowhead shaped muzzle brake seen on Barrett 50 caliber Sniper Rifles, or the Molot GK-01 Muzzle Brake that is often used on the Molot Vepr-12 shotgun. A muzzle brake works by redirecting the gases that exit the muzzle upwards and/or to both sides thereby effectively controlling muzzle rise and helping to control recoil. Controlling these two forces helps to keep the shooter on target and aids in faster follow up shots. Although often confused with each other, the flash hider is meant only to reduce the amount of flash from the muzzle to protect the shooters night vision and reduce his visible signature to enemy forces, and the muzzle brake is meant only to reduce recoil, muzzle climb, and usually does not help to reduce flash by an appreciable amount.