It depends on his size and stature. At 14, I could shoot a 12 gauge loaded with buckshot like a BB gun. On the other hand, I had a friend who would shoot the same gun and it would put him on his ass. If he is a skinny little guy, I suggest getting something just a touch weaker, like a 22-250, or .270; these rounds also have very flat trajectories. If he's a big guy like me, go for a 30-06. It's the most powerful common hunting round, and I have seen deer shot in the legs with these things die of blood loss and trauma. Some people might say .308, but there is NOTHING a .308 can do that a 30-06 can't do 400fps better. Plus a 30-06 is also capable of bringing down moose, unlike other common cartridges. The next step up from this cartridge is the .338, and I doubt you have that kind of money. I know I don't lol.