I think there are several reasons to doubt that it is physically
possible for people to feel the speed of powder as directly driving some "recoil impulse," particularly in handguns. Before I get started, I should emphasize that I am
NOT saying that different powders don't produce different levels of recoil (both real and perceived). They do. That's not what I am saying. What I am saying is that I do not believe that humans - any human - directly perceives the speed of powder in a way that would lead them to experience slower powders as being gentler and faster powders as harsher. I contend that
cannot happen.
Reason one: Human perceptional time is not infinitely fast. It takes time for our brains to collect sensory data and perceive it. When sensory inputs are briefer than the "refresh rate" of our perceptual machinery, we often end up with a summed-over-time perception. We're all familiar with this in the context of sight, where still images flashed in chunks of ~40 milliseconds get blended together into moving images - TV and movies rely on this. This same phenomenon occurs with other sensory inputs, and touch is included. The difference in where a pressure peak occurs between, say, fast and slow pistol powders, or how spread out it is - that's a difference of far less than a single millisecond. The whole "dwell time" in the barrel isn't long enough for us to "feel" the recoil in real time - the bullet is gone before we even perceive the recoil.
Just look at this chart, showing a load of HS6 (a fairly slow pistol powder) and Win 231 (a faster powder):
Bearing in mind that the whole window of perception for humans is longer that this entire graph, I find it beyond implausible that someone could feel the difference in the spike-versus-tail shape of these two curves. No chance. Now, I
do think people might be able to perceive the difference between the total area under the curves, or even the pressure-at-exit... but the shape of the curve? No chance.
Reason two: Even if you had a mutant human with some kind of superhuman touch-perceptional time frame/refresh rate, the design of a modern browning-type semi-auto handgun simply does not transmit recoil information to the shooter in real time. Look at this video (fast-forward to the 0:10 mark).
Notice that the bullet is
gone before the slide has moved a quarter inch. Even when the slide is moving during recoil, it's only transmitting force to the user through the spring... the spring is compressing, and buffering that force until the slide hits home at the end of travel. The powder has long since either burned or left the barrel by the time the frame begins any kind of significant movement in/against the shooter's hand. Here's another video (of a shooter with a pretty floppy one-handed grip):
Again: The powder is burned and the bullet is gone
before the shooter starts to experience any serious level of recoil. It's somewhat similar to a car traveling down the highway that hits a moderate bump - by the time the driver's seat moves (much less moves enough for the driver to feel
and for enough time to have elapsed for the driver to "feel" the bump), the car's tires are well past the bump. The energy goes into the suspension's springs and shocks, and those
eventually transmit some of the force to the frame of the car, which then transmits it to the driver's rear end.
There are other reasons, but those are the two primary reasons I say there is
no way that people feel a "longer" recoil impulse with slow powder in a pistol or a "faster" impulse with fast powder. Not possible either as a matter of physics nor physiology. (Golfer's can't "feel the ball on the face of the club," either. The ball's long gone by the time the vibrations make it up the shaft and communicate contact quality to the golfer.)
