How old/big is your son? I think one should start getting good with full powered bolt action rifles as soon as they're physicaly fit to do so. Even if something less powerful is sufficient, the full power is better IF he can handle it. Of course, I started shooting at 18 and 165lb, and never had the experience a rifle being too powerful for me (course I never fired a .460 Weatherby Mag, or a BMG... fired a .458 though). Certainly wouldn't want to turn him off from shooting by overwhelming him.