I dropped my first moose with a 32-20 rifle, but had to finish him off with the .45acp. Every elk and moose I've taken has been with 30-06, 180gr Sierra BT at ~2750fps. I switched to 220 Barnes for the Grizzley and the Polar Bear.
A friend dropped by one time and flew me up to a pair of dumb-bell ponds where he had seen some carabou. We landed in the empty pond and sneaked up to the edge of the populated pond. Friend had 13 tags and I had 4. We agreed on the split in who would shoot how many, based on our respective magazine loads and started taking winter meat. After the noise stopped, I heard friend cussing. "We dropped too many!" I counted down animals and, yep, we had two more than we should. We both started gutting and I heard him yell again. He had grabbed an animal by the antlers and it stood up and took off. So did the one next to it.
We decided that those two had seen all the others lying down and decided to take a nap, too.