Re: .223 vs 5.56 Chambers - HUGE bullet jump?
If you're fairly new to the gas guns, it might be worthwhile for you to take a look at Glen Zediker's book, "Handloading for Competition." Glen deals with Service Rifles at length, and it really is a very different world than loading for bolt guns. Some things which we take as critical for "normal" reloading become completely irrelevant, and in some cases, downright problematical. Others, which you have some latitude with in bolt gun reloading, suddenly become critical (such as full length sizing, shoulder bumping, etc.). Bottom line is, they're different, and can't be approached the same way.
The AR is an inherently accurate little rifle, and with a few refinements (such as the float tube and a decent trigger), they're simply phenomenal. They've completely displaced the larger 30 caliber Service Rifles in competition these days, and they serve as the basis for some very accurate varmint guns. A friend of mine, John Feamster, actually shot one in a registered BenchRest match some time back. This wasn't well received by the other competitors, who tried to throw up some roadblocks to keep him out of the match. Nothing in the rulebook prevented it, ans when he cheerfully agreed to use a brass catcher to prevent his ejected cases from annoying the other shoters, they grudgingly let him pay his entry fee and shoot. They were even less amused when during one of the first relays, he fired an "Official Screamer" group; a group fired in a registered match measuring less than .100" at 100 yards, .200 at 200 yards, etc., for which an award is made. He didn't win the match, but he did beat several bolt gunners, and placed somewhere in the middle of the pack. Not too bad, considering the company. They also made it plain that he wasn't really welcome at future matches. Hey, some folks just can't deal with progress.