the only truely quiet muzzle brake (other than silencers/suppressors which also act as brakes) I have ever even hear of was manufactured by an outfit called american safe arms. The way they did it was fitted an oversized sleeve about the size of a 10 gauge barrel around a lightweight barrel and vented the gasses into the sleeve. they ended up in trouble with the atf for a little while cause the atf decided they were building silencers not muzzle brakes. As the story goes browning was interested in the technology and loaned them their legal staff. They reached an agreement with the atf that they would tune their brakes to lower the overall noise no more than 4 or 5 decibles and the atf would classify them as brakes. It wasn't too long after this that they seem to have dissapeared. i have often thought that would have been the brake to have. All this is just going on memory so take it with a grain of salt.
