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I'm thinking the RS2 is just an AR1000 if I recall right.I still have one more piston with the original seal on it from the Black Ops. (Same thing as the RS2 but no dovetails and not a swappable barrel)That PA seal does take the same type screw. I'd gamble on it knowing that I'd have a 33% chance it was a drop in.There's also a 33% chance it needs resized to fit. Then another 33% chance it's to small.So you have a 66% chance it will work.