I'd be looking at the .338-06. I had one in a fairly light rifle, it was extremely accurate and easy on the shoulder. With the .338-06 you'll going to get an extra 200fps. out of it. I think that you ought to be able to get more yardage out of the .338-06. The .338 Federal is a great cartridge too. Presently my go to rifle is a 35 Whelen, wouldn't trade it for anything. The back-up rifle to that is a .358 Winchester, either of these two cartridges are really accurate and "bang-flop" at 300 yards. The .358 Winchester has fallen to the "bad-press" syndrome, it doesn't get the recognition that it ought to get. Most of the press that it out there is that it is a great, short range, brush busting cartridge that has a lot of recoil, not true at all. I am ole school and do laud these older cartridges. I also like the .270 Winchester (just built a .270 Ackley Improved), the .308 Winchester and the 30-06 equally as well. As for long or short actions, if I were building the .338 Federal I would stick with the short action. One of the reasons that I like my .358 Winchester is that it is a short action, easy handling rifle that packs some horsepower. From what I have seen the heavier bullets "might" would not be my choice, I'd stick with the 200/210gr bullets, thus you wouldn't need the long action. IMHO & .02ct worth!