If you're NOT going to handload, Go with a 7mm-08 and buy Hornady 120gr SST Lite ammo until he's use to it, then you can go to full grown 150 grain loads (or whatever) in the next 2 or 3 years. Kids that age when I grew up were shooting 12 gauges. You could even get away with going with a 308, since Hornady makes the Lite ammo for it, too, and the 308 is capable of taking anything on the continent. Remember the 7mm-08 was developed by target shooters because of its accuracy and ability to get to 1000 yards, granted you'd have to have an 8 Twist barrel to do that. I'd look DARN hard at the Browning Micro Stalker, Hunter, or Medallion.