Clamps on to A2's
http://www.griffinarmament.com/Griff...d-p/gaqdbs.htm
It wouldn't be quieter, but it would direct the muzzle blast a little farther away from the shooter, which might make it seem a little quieter.
If you light up a gun with a linear comp or blast shield or whatever in an enclosed space and it's still going rattle your teeth. It's more of a range item IMO.