Deer gun advice.

My Brother is just getting into a deer hunting. Lives in Indiana, but may hunt in Northern Michigan with me. I’ve always used a 20ga shotgun or a bolt action 30-30 depending on the terrain. Practically, I want to advise him to get a 12ga pump. However, he seems pretty intent on a rifle for the longer farm shots in Indiana, but still wants a round that is be effective in brush in Michigan. Any suggestions? Maybe .450 bushmaster?