I hope someone can help me understand the NBRSA rule regarding muzzle brakes. I get the impression there is as much an attempt to comply with the spirit of the rule as much as to the letter of the rule. I think I understand a muzzle brake that has ports less than 90 degrees relative to the barrel will obviously deflect gasses to the rear and so be illegal. The rule prohibits clamshell or any other device that causes "any" gases to vent to the rear. To me any means no gasses rearward. There are devices that have oval ports and round ports at right angle to the barrel. I have experienced blowback from both devices. However I have heard from shooters that round holes in the brake are ok while oval ports, sometimes a tactical style, are prohibited. I know we don't measure blow back from both styles so how does one comply with the rule without offending the more sensitive shooters?