I agree with (MOZIYINMORIN) .243 is a good starter for the youngster. When he's proficient with that rebarrel it up to a .260 or 7-08.Thanks everyone. I appreciate the input.
I wouldn't put him on a rifle that might give him a bad flinch habit.
Start at the bottom of bullet weights, and as he gains confidence move up in bullet weight.
Flinching is a very hard habit to break