M1 Garand. Get a fun, full power piece of history from CMP for about $500 (unless they have gone up, I havent looked since I got mine a year ago).Also, Enfield No4 MKI's (probly some of the other Enfield models, but I cant say for sure, as I only know about the one I own) can be had for about $200, and .303 Brit certainlys isnt a bad round at all.Both guns are fun, have some deep history, are cheap, have peep sights, and can be quite accurate if you examine and select them carefully.That said, if your purpose it to train/practice for Army boot camp, the best is probly just get a cheap used AR to get familiar with cleaning, disassembly/reassembly, the sights, the ergonomics, etc.I wouldnt worry about trying to learn TOO much though, as the Army will have its own way of doing EVERYTHING, and you WILL do it that way, whether its the best way, or what you like or are famimiliar with, or not.(unless the Army is different than the NAVY.I learned in boot camp that in spite of what I though from the 27 years I had been alive,I didnt know how to make a bed, fold clothes, eat, sleep, satnd, walk, run, shower, speak or write properly until the Navy taught me how to do it.
Enjoy! boot camp (or whatever the Army may call it) is a unique, once in a lifetime experiance unlike ANYTHING you have ever done or imagined, that you will love, hate, and certainly NEVER forget.