RE: Gun for my son??
It's hard to beat a .243 as a "first rifle".
- bullet weights are available (even more when handloading) to handle everything from prairie dogs and coyotes through deer and antelope.
- it's the minimum legal caliber in many states (i.e. - if he can't handle a .243, he's probably not ready to be afield with a tag)
- if he one day decides he's ready to start hunting moose or elk, he'll have an excuse to buy a bigger rifle (.30-06, .300 Mag, etc.) - and will still have a deer/varmint setup in the .243.
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Oh, and for the last reason above, I'd lean toward a bolt-action sporter. A number of "youth" model bolt guns can be updated with an adult-size stock laterif need be. Though I won't argue that a single-shot will makehim a bettermarksman, you can achieve the same effect with a bolt-action repeater by giving him a single round at a time to chamber and fire.