It's been a long time since I loaded for a G22, but I had no troubles with it. It wasn't accurate enough to suit me but it ran 100%.
What I DO recall about the .40 is that if the bullet sets back in feeding, pressure goes up rapidly, and it does not take a lot of setback to cause significant pressure rise.
Dave Scovil of Handloader discussed this topic, and while he was interested in the accuracy of .45 Colt loads, the same lesson applies I think to autoloaders. You want a tight fit of bullet to case, and the expander plug should be at least .005" smaller than the bullet diameter, AND firmly taper crimp. When you are done, you should be able to press the cartridge firmly against a solid object, bullet first, and the cartridge OAL should not change more than a couple thousandths.
Possibly the OP had some setback, combined with less than optimum cases, and less than optimum case support.
A lot of things are "possible".
Working with facts and not possible/guesses is how you make improvements or reduce risks.
Every cartridge will have internal pressure rise when there is bullet setback and reduced internal capacity. That is not exclusive to .40 S&W or any other cartridge.
Going back to square one, loading wise, as mentioned earlier in the thread and inspecting your reloading procedure and equipment is generally a good starting point. Making sure the rounds are being produced with clean equipment is part of that procedure. Inspecting the firearm and brass may tell you other things.
The fact is that unless a person has the actual firearm as well as the brass at hand, trying to determine a cause as to why what happened, happened, it is pointless, and people are just making unsubstantiated guesses. Usually those are based off of "I read this".
I have read a fair number of articles by guys in magazines/online articles and I will say that a substantial amount of them are either completely making crap up, or they are cut and pasting their "expertise" from somewhere else and a good bit of it is simply wrong. That information then gets repeated on online forums. "Joe gunwriter says that .44 Magnums are not lethal past 75 yards, and you can't hit anything with a handgun at 100 yards".
