Barrel length for minimum noise

[21contender]

Personally, I like my 21" barrel length. On the contender frame, the 21" barrel still makes a handy, short rifle. A bolt gun would be longer but I still think getting the muzzel as far from your ears as is reasonable would be a good thing. The countersunk crown sounds interesting. That might act some what like your "bloop tube" from a previous post. The crack you mention in that post comes more from the supersonic bullet than from powder gases.