Several posts recently asked about barrel weights. Below is a link that will take you to a calculator. Simply plug in the size of the octagon across the flats, not points, then do the same with the bore size as a circle and subtract the results. You can get the results in inches, feet or yards. Also, it works in metric sizes too.
It will be slightly off because you can't figure in the rifling, but that will be very minimal.
http://www.matweb.com/tools/weightcalculator.aspxBill
