It's justmy opinionbut you need to get him a 20 gauge. It'll be almost as light and easy to carry for him while the 20 gauge will be MUCH more effective on deer size game. It would be devastating for him to shoot a deer,only to have it run off and be lost. Sure,under optimal conditions,a .410 will kill a deer but why take the chance? A 20 gauge single shot won't break your bank either. A LOT of people have the misconception that a .410 slug "shoots as hard as a rifle" while nothing could be further from the truth. I started all my kids out on 20 gauge after they learned how to properly and effectively handle/shoot a .22 rifle.