Tom,
I understand the relationship between mass and inertia, so when you are doing this test, maybe you could try the compact with a full mag and the full size with just one in the pipe and an empty magazine.
If the slide and barrel difference matter that much (your testing will show us) then someone shooting a compact could add weight to the gun (weapon light or just clamp a weight on the rail) while at the range to reduce the felt recoil.
Could be a million dollar idea.... The Lower Recoil-inator!![]()
One factor with compacts (a big one) is that the short grip affects recoil control. I believe the M&P compacts have a floor plate extension to get a full shooting grip. That should help. Of course it also makes the grip length closer to the full size gun which sort of defeats the purpose.
A few years ago I went thru all of this with a Kahr K9 and K40. The K40 murdered my shot splits for a given level of combat accuracy compared to the 9mm. As for the M&P, I've only owned the full size 9 and 40. Maybe the compact M&Ps defy the laws of physics.
