love this post....its kinda 'my thing"....when your dealing with an AR platform, it all comes down to how much money you want to spend. if you want to go all out and buy the absolute best USA made rifle, then look into LRMC. get ready to spent 1500-3000 dollars for a base rifle though....if you want to stay affordable, my opionion of affordable anyways, look at the BCM (bravo company) carbines. they have extended heat treated barrels and gas tubes. you can pick those up for around 1000 bucks for a base rifle. i carried a department issued rock river arms for years and really had no complaints with it...it did seem to hold a little more carbon build up, but that could have been the cheaper loads that we were issued for practice rounds. I personally, my opion only (coming from twelve years law enforcement and spending six years as a SWAT team leader), i would stay away from smith and wesson m&p rifles (or handguns), they are built really cheap and there performance shows it. DPMS, Colt, and rock river; i wouldnt consider a "low quality" carbine, but a lower quality than LRMC or BCM. I have never shot the Remington R-15, but i do like the caliber options you get with it.
the above is strictly my opions....