If I already had a long Mag I would not switch. If I were buying a new mag then I would go with the short mag. My choice of all of them is the 270 WSM. Pretty light recoil but a 200-250 fps gain over the standard version. Your friends 308 will work fine for elk as well. A friend of mine borrowed my 260 Rem with 140 grain Barnes X bullets and took a very nice bull elk in Wyoming last fall. I charged him some elk steaks for rent. He broke the elks shoulder and as they always do, the X bullet exited the far side.