Acording to my 2001 copy of the rules, the use of compensators, muzzle brakes and barrel porting is prohibited. The adjustment holes on the Boss-CR are not considered to be compensators, muzzle brakes and barrel porting.
For HP Hunting Rifles the rule said "A factory installed tuner that is a catalog item and that does not work as a muzzle brake is permitted." But the "factory installed - catalog item" requirements probably went away when they loosened up the hunter class rules last year. Perhaps someone with a new copy of the rules will chime in.
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