one opinion on caliber from a Canadian outfitter
Be aware that moose are big animals and your choice of caliber should be leaning towards the heavy end of the scale. The .30-06 with a 180 grain bullet is about the minimum that we like to see in camp. Any of the thirty caliber magnums are good, with 180 - 200 grain bullets, as is the .338 with 210 - 250 grain bullets. The various .35 calibers from the .35 Whelen and up are not out of place here, either. In all cases, use well-constructed bullets"
Just my 2¢.