Ive been playin with AR's for years.
I (or the wife and one of the kids) currently have lowers from the following manufacturers: Bushmaster, DPMS, STAG, R guns, Rock River Arms, and Fulton Armory. Of those, I have gone into and fixed or changed or outright built from each of those recievers. Other than the finish or some mild "tweeking" all perform and are as dependable as the next. Some have as little as a few hundred rounds through them while others have over 8000 rounds through them. I have had to send back recievers from Olympic because I couldnt get the mag release to line up correctly nor could I get the bolt catch pin to line up correctly so if you cant get your pieces to go in, there isnt much sense in keeping the $75 paper weight.
"Who are the militia? Are they not ourselves. Congress have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birth-right of an American...(T)he unlimited power of the sword is not in the hands of either the federal or state governments, but, where I trust in God it will ever remain, in the hands of the people." (Tench Coxe, Freeman's Journal, 20 Feb 1778)