[Magnum44]

a “shove” recoil is more tolerable than a “slam” recoil.

True

Buffer assemblies trades the magnitude of the recoil impulse for the length (in time) of the recoil impulse.

Partially true. The stored energy in the spring is also used to drive the BCG forward and load the next round.

[NorthMountain]

Energy and momentum are not the same thing.

The stored energy in the spring is also used to drive the BCG forward and load the next round.

True, but not relevant to the backward recoil impulse. The bolt/BCG being driven forward introduces a new impulsive force which further drags the whole business out in time.

BTW, you've just given me an idea for suggestion to "Ballistic High Speed" or "The Slow-Mo Guys" ... their kind of high-speed video of an AR-15 (or some such) firing when shouldered, and when hanging freely. I'd like to actually SEE (at ridiculous frame rate) the recoil motion of a rifle. A gas-operated semiauto should be very different from a bolt-action.