I think most people will agree that the gen4 guns have less felt recoil than the gen3 guns. I'm trying to figure out what it is about the duel RSA that makes this happen. I've been told that in a single spring set up, a lighter spring yields less recoil but more frame battering. My gen4 21 seems to have a my stiffer spring than my gen3 21 but at the same time seems like it does have less recoil. Does the gen4 RSA start stiff then get light? How does it get the lighter recoil while at the same time feeling stiffer?