Two points: If the shot load hits an immovable obstruction in the bore there should be movement off the shoulder as the inertia of the moving load should be pushing the gun forward. However I doubt anyone notices it just as the barrel rips open.

Second point is if pressure itself produces recoil as Chuck believes then he should be able to also feel the barrels moving upward and downward at the same time in his hand as the pressure is acting with equal force in all directions. And with more surface area of the barrel sides involved than the area of the standing breech, he should feel more of this recoil in his forward hand than his shoulder.

I will stick with the law of physics and continue to believe recoil is a function of velocity produced.

REVDOCDrew I don't discount your antedotal incident. However, you need to compare equal velocity loads in both lengths (and blind so you don't know which is being fired) before the test would have any significance.