what's funny to me is, I spent 5 days at devens with my reserve unit...3 were basically full days of shooting. there was a time or two or three that I caught myself without hearing protection on when firing commenced and it wasn't all that bad. that being said, whenever i'm at the range at home, if someone has an AR with an MC...it's fairly likely that I choose to go to another part of the range until they're done shooting.
I don't know what the difference in actual dB rating is between a birdcage and a MA compliant brake, but the same exact damn ammo out of a civilian AR seems to have enough percussion to make ME jump! how one AR can feel louder than 30-40 M16's shooting at the same time is beyond me. i'm sure some of it has to do with the physical layout of Golf range @ Devens vs. WP&R club with berms in pretty much every direction except up the driveway.