The Rock River 2 Stage NM Trigger is actually a 4 1/2 lb NM trigger. They have to measure that due to the fact they use them at Camp Perry for the National Competition and it specifies a 4 1/2 lb. overall trigger pull to be legal for the match. They have 1 Lb on the First Stage = (Free Travel). And as you stated 3 1/2 lbs on the Second Stage. (Let Off) And as Jon stated the only difference is one is obviously Chromed and the other is not.
Either one is a fine trigger! I guess if you want the chrome for cosmetics that would be good. Some buy into the chrome is smoother? Questionable at best! When the standard one laps in at about 300 rounds they are smooth as silk. When you first get them they are actually around a 4 3/4 lb. But lap in at the specifications above being 1 lb and 3 1/2 lbs. As I said both are great triggers. I have them also in most of my other ARs.
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