Disadvantages
The advantages of brakes and compensators are not without downsides, however. 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 sound, flash, pressure waves, and lead loaded smoke plume normally projected away from the shooter are now partially redirected outwards to the side or sometimes at partially backward angles towards 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 towards the gun crew or spotters by arrowhead shaped reactive muzzle brakes found on sniper team fired anti-materiel rifles like the Barrett M82.
Read more about this topic: Muzzle Brake, Utility