i've long felt that aspect of recoil isn't given enough attention. rather all the emphasis is on the raw # of ftlbs. but just as the math for kinetic energy of the projectile (bullet, shot, whatever) is biased towards velocity, so is it for the gun. 50ftlbs of recoil in a light gun compared to the same 50 in a heavy gun is going to feel totally different and my impression has been more uncomfortable. the light gun being a much more abrupt, harsher jab and the heavier being a slower, longer drawn-out shove.
i happened to realize when i said 30ftlbs for a 6.75# 12 ga i was basing that on 1-1/4oz and 3-3/4 dram loads. that's not really 3" mag. i've got an excel spread sheet done up to calculate recoil energy, gun velocity, and gun momentum and only have to input the projectile weight, powder weight, muzzle velocity and gun weight. don't have load data handy for 3" magnum 12 but i'm betting between a 3" mag 12 at 6.75# and an 11# 470 the difference will be less than twice and i'd not be surprised if the actual "felt" recoil difference were even less than that. i'd expect a 6.75# gun firing 3" mags would have rather brisk recoil. in fact, it looked like the velocity of the recoiling firearm would be almost the same for both. the rifle would still have a faster acceleration to that velocity but also has almost double the inertia to overcome before it even starts moving.
roger
