Looking for some help. I took some Hornady light mags 139gn to the range, and very impressed by the accuracy of my rifle. My question is, I shoot a Rem M7 in 7mm-08 that has a 20 inch barrel, and Hornady advertizes 3000 fps from their loads. I need help in determining what speed I could expect from a 20 inch barrel. My guess, is Hornady used a 24 inch barrel to produce 3000 fps. Any help would be great.....

R1