Granted you don't gain with a shorter action, but if you put a 338WM or a 340WBY in a compact 20 inch barrel, use lose lots of velocity, and gain muzzle blast. These cartridges shine with a 26" barrel. Again, the 338RCM was invented around a 20" barrel. OK, how about they they chamber it in the MKII 77 RSI. Then you are getting a shorter action with a short barrel. I would like to see either, although I would prefer the single shot.