I have had three "improved" 280's, two AI and one RCBS. I have also shot a 280 a lot. My 280 with a longer throat, OAL 3.45, is about 30-35 fps behind the "improved" cases at equal pressures. In a hunting rifle, I would use a 22-23" barrel.
The reason the improved cases are more difficult to get to feed as slickly as a standard is because of the reduced body taper. The shoulder angle has nothing to do with that other than most "improveds" have both.
Also the idea that a 280 AI is lighter than a 7 mag is just wrong thinking. Same stock, same barrel, same action...the magnum will be slightly lighter because the chamber removes a little more steel.
I would get the standard built but have the throat extended. Cases and dies are cheaper. Or just get a 270 or a 7RM.
I've never seen a factory barrel chambered for magnum that didn't haven't a heavier barrel contour (longer shank) than the same rifle chambered for non-magnum rounds. Why do the factories do that ?
