Up here in Canada we shoot some of the hardest and heaviest animals, if you stick with just a plain 300 win mag its great. No need to go up from there for north america. And yes a .270 will take down a moose and fast! Used one for years and wish i had never gotten rid of it, best gun ive ever had. But no you definately dont need to go Ultra, standard mag is great , not sure about short mag, never shot one, but i think shells are quite a bit more for one.