Here's an interesting read on tuning a barrel. I've also read that if you sprinkle talc powder on you barrel and hit it to make it vibrate, the talc will accumulate at the node. Any experts out there that can verify this?
http://www.precisionshooting.com/psm_2005_03_issue.html
http://www.precisionshooting.com/psm_2005_03_issue.html