A solid bullet 150grs or more will do it, what cartiage does your rifle chamber? I suppose it won't be any overly long shot in Maine? So don't need any huge rifle pretty well any .30 will do the job (even a .30-30 will do it, but I won't try), you can go down to a .270, but thats about as small as most people should use for a moose. But you don't need a .338 or bigger.