See post 5.
I’m wondering if both have same recoil springs? Maybe the NH has a flat wire one? Or one has a slightly different recoil system setup?
This was my first thought. All else being equal, wouldn’t spring rates and wear of said springs have some affect?Recoil spring weight, mainspring weight or the profile of the firing pin stop could be playing a role in the felt recoil of each pistol so it isn’t as cut and dry as the heavier gun will always have less felt recoil.