RE: 45-70 for 16 year old
You can shoot a couple of boxes of the Remington .45-70 ammo with maybe a sweatshirt on and you probably wont even bat an eye. Guys at the range thought I was nuts once I was shooting mine in a long-sleeve t-shirt. People who dont know any better hear .45-70, and they start looking at you like you're shooting a .700NE from the hip.
Like Co.Elk said, there's plenty of ammo out there for this gun that will be good for elk and moose. It'll kick a good bit more, but just get used to shooting the Remington stuff first and work up to the heavy stuff.
PABigBore