Thanks for the advice.Like the first poster, the Ruger is very heavy (front heavy) and feels odd to me to shoulder because of that. I own the M&P 15T and have shot the Ruger 556 and like the 15T better because of the weight/balance. As for actual shooting, they perform the same, no felt difference or accuracy difference. The Sig 556 is the same way, oddly heavy in the front and I don't like shooting it as much. Little clumsy and heavy when carried in a grocho style walk/shoot situation. I always pick one of my direct impingement AR's over the piston style just becuase of those factors.