You actually need two guns. I personally have never been satisfied with small grain bullets on larger calibers. The 243 will kill sheep, but on long shots you need something that will anchor him pretty quick. The 270 would do this. As far as deer, varmints and coyotes, .243 is good choice. Personally, if your going after sheep in Alaska, I wouldn't use anything less than a 30-06. You will probably be in mountain grizzly country and a .270 might be light on charging grizz. HH CG