Somewhat agreed, and that's one reason you might feeling less recoil from the larger and smoother bore of your shotgun w the same projectile weight. I think the twist factor/friction might be noticeable when comparing a rifle w a shotgun. Also, much of the recoil is generated by the projectile's exit from the muzzle. That's why muzzle brakes work on the new fangled stuff. It redirects the exit gasses to pull the muzzle forward and down instead of pushing the shooter back. Reduce the pipe, use the same weight projectile, same charge, the pressure is amplified at separation. Probably a combo of other things mentioned here as well. A smooth bore would not necessarily produce more velocity because that becomes a function of the pressure curve, rifling/friction and propellant dynamics. I will leave that for the black powder experts here on how that translate w ML's, smooth vs. rifled, but w smokeless, this is why there are so many different burn rates designed to get the most from these peculiarities of a given rifle. 2 different rifles, same bullet, same caliber and even same exact model-surprisingly different powders can be best for each. Same powder- way different performances. Bore tightness, chamber differences and other factors from tooling differentials are huge. I think that part holds true for ML's as well. SW