At what barrel length (actualy it's expansion ratio) do you no longer get a velocity increase? Is there a formula for this? I got into this discussion on another board, and my "senior moment" memory came up with a 50/1 rule of thumb. It is a friendly discussion, so if I was incorrect I won't be pilleried over their. The deep ballistics expertese, and friendly nature, of this board led me to post here instead of on one of the "bubba-n-buddies" boards.