The shooter, gun crew, or close bystanders may perceive an increase in sound pressure level as well as an increase in muzzle blast and
lead exposure. This occurs because the pressure waves (including sound), flash, and lead-loaded smoke plume normally projected away from the shooter are now partially redirected to the side or sometimes at partially backward angles toward the shooter or gun crew. Standard eye and ear protection, important for all shooters, may not be adequate to avoid
hearing damage with the muzzle blast partially vectored back toward the gun crew or spotters by arrowhead-shaped reactive muzzle brakes found on
sniper teams firing
anti-materiel rifles like the
Barrett M82. Measurements indicate that on a rifle, a muzzle brake presumably redirecting its gases at least somewhat backward adds 5 to 10 dB to the normal noise level perceived by the shooter, increasing total noise levels up to 160 dB(A) ± 3 dB. Painful discomfort occurs at approximately 120 to 125 dB(A), with some references claiming 133 dB(A) for the threshold of pain. Brakes and compensators also add length, mass, and typically diameter to the muzzle end of a firearm, where it most influences its handling and may interfere with accuracy, as muzzle rise will occur when the brake is removed and shooting without the brake can throw off the strike of the round. A serious tactical disadvantage of muzzle brakes on both small arms and artillery is that, depending on their designs, they may cause escaping gases to throw up dust and debris clouds that impair visibility and reveal one's position, not to mention posing a hazard to individuals without eye protection. Troops often wet the ground in front of antitank guns in defensive emplacements to prevent this, and snipers are specially trained in techniques for suppressing or concealing the magnified effects of lateral muzzle blast when firing rifles with such brakes. The redirection of larger amounts of escaping high-pressure gas can cause discomfort caused by blast-induced
sinus cavity concussion. Such discomfort can especially become a problem for
anti-materiel rifle shooters due to the larger than normal cartridges with accompanying large case capacities and propellant volumes these rifles use and can be a reason for promoting accelerated shooter fatigue and flinching. Furthermore, the redirected blast may direct pressure waves toward the eye, potentially leading to
retinal detachment when repeated shooting is performed with anti-materiel and large caliber weapons. == Ported chamber ==