These guys have given you good advice. If you can try out some before you buy, that would be the thing to do. You really don't want to develop a flinch when you are getting started, and the 06 does have a pretty good kick. My cousin just got a .243 for his twelve year old who is about your size. It is a Savage "youth" model. Most of the gun makers produce rifles that are designed for younger shooters like this. This usually means a light or moderate recoiling caliber and a shorter trigger pull (shorter stock) and lighter overall weight. Calibers that can kill deer very nicely are: .243 Win, 6mm Rem, .260 Rem, 7mm/08 (in order of bullet size). In fact, the largest elk I ever mounted in 25 years of professional taxidermy was killed by a sixteen year old kid with a .243 - dropped the huge bull dead in its tracks with a heart shot. Remember a well-constructed well-placed bullet of any reasonable caliber will knock the socks off of any big game animal and a bad hit with any caliber is still just a bad hit! My best advice is to get one with a good safety (some are better than others) and that can be unloaded without having to work the bullets through the chamber. Stay with a bolt action and put a Limbsaver on it no matter what the caliber. Good luck, little buddy!