m4carbine.com is a great forum for finding out all things AR. Check out the 'Chart', I believe it's under general discussions, to get your questions answered. BM, as are RRA, is a good choice for the target shooter who doesn't depend on their rifle in a combat situation.

Also check out CMMG's bargain basement AR's. As new blems, etc. Around 600.00. I think PitBull of Love or his brother posted their's a while ago. Now that's a deal. Do a search and you'll find it.

Can't go wrong either way.