Ruger AR 556 vs. SR 556.

[GMAN_R]

What's the main difference? I see the barrel twist rates are different. Is the AR 556 a direct impingement gas system whereas the SR 556 is a piston rig?

 

[JoeBobOutfitters]

Apples and oranges.

AR556=cheaper and Direct Impingement (very popular)

SR556=more expensive & piston (not real popular)