I took my Fulton Armory Guardian M4 upper and decided to see what it would do at 100 yards.  I used Remington Golden Bullets and shot from an elbow rest. I used the existing wide front sight and a carry handle NM sight.  I was able to shoot three inch groups!!!.  This wasn't with three or five rounds, this was with two 10 round magazines.  And the Ciener ran as smooth as i have ever seen.

I tried this in my RockRiver NM Upper and could only get 4 Inch groups at that distance and it has a 20 inch free floated barrel and NM Front and Rear sights.  Wow this FA upper is awesome!

I next tried some reloads that I made up using surplus, pulled bullets from Wideners and 2200 powder that were made for my other Colt AR 15.  With my OKO sight set to level five, in bright daylight, I was able to shoot a two inch  twenty shot group.  

I am one happy dude, hurricane and all.

John from MD

What are the twist rates of the barrels?  My experiences have been that the twist rate of the barrel has a significant impact on the achievable group size.

If both uppers have "stock" bbls, the Guardian has a 1/9 and the NM has a 1/8. It would make sense the the 1/9 is a little more accurate. AFAIK, dedicated .22LR conversion bbls have a 1/16 twist.