I have a SKS, that shoots 7.62x39. When I go deer hunting it is a very common rifle, same as a Ruger mini-30 (which shoots the same size bullets) and a 30-30 lever. All of those rifle are around the same power, and I would for sure go hunting with any one of those for Moose, if my main Moose rifle was acting up. I always bring along my SKS for a backup rifle if someone in the group needs it. I would'nt take a 200 yard shot on a Moose in wide open clearing, but at 100 or so, go for it. A couple quick pops, and there would be fresh Moose on the BBQ.
If you have the means though, a .308 or even better a 30-06 or .300mag would be much more better suited for hunting moose. I would'nt go any smaller than a .308 though if you were going out to buy a Moose rifle for that purpose.