You've got something in front of the Muzzle Brake on your gun? If you are referring to the crush washer behind your muzzle brake, (AR15?)
I've had very tight Nylon washers split like that, before. Might it have been over-torqued? Firing the gun on a over-pressured washer could do that,
but AFAIK it probably is mind over matter, if you don't mind, it don't matter.