Magnum rounds in short barrels

[L. Cooper]

I think accuracy may be irrelevant in the shorter barrels, but velocity loss will be enough in a 20 inch that the whole advantage of the magnum will be lost. Certainly the 7mm will lose from 30 to 50 fps per inch off of a 24 inch barrell. Take off 200 fps from the 7mm Rem Mag, and you have the .280 Rem.

Not so sure about the .338. May do better because of the larger barrel diameter, but it will still lose velocity. My take is that if you are going to shoot a magnum, you need 24 inches (or more) to make it worth the effort.