Looking for a standard 20 inch A4 upper from  RB Precision, M&A Parts and Model 1 parts. Prices are about the same. Rb says they use a wilson chrome moly 1:9 or wilson air gauge stainless 1:8. barrel.     M & A Parts says they use a wilson chrome moly heavy match grade barrel 1:9 or 1:7.      Model 1 Parts says they use a heavy chrome moly or stainless steel in 1:9 or 1:8. Ok guys if i want to shoot a variety of ammo which one of these uppers would you choose for accuracy and reliability. THis is driving me crazy.I cant make up my mind and i cant buy all three. I have a complete Rock River lower waiting for an upper....

I'll give the standard ARFCOM response, buy both and post pics.

RB sells RRA , so keep it all Rock River. I think the bolt and carrier  will be better quality

The 1:7 barrel from M&A Parts is chrome lined and purportedly USGI spec.  I've been thinking about one of the kits and would sure like to hear from anyone who's tried one.