I've heard of people misloading .40's in their .45 mags, and they actually sort of work, kinda, sometimes. That's why I label everything, including the mags.
Had a friend tell me he had problem with his "new" 9mm. It would fire one shot and not eject or load another round. He shot one round at m range, I looked at the empty brass all buldged and had him turn the gun over and showed him why. It said 40 S&W on the slide!!
Having a gun doesn't make you any smarter. And stupid mistakes still happen.
I've been shooting for over 30 years.
Still managed to put some .40s down my new 1911.
Learned my lesson.
When I cleaned a range for my job, I would find quite a few of those .40's swelled out in a .45 chamber. In addition I found 9mm brass that was fired in a .40 chamber. I also found .44 magnum brass slit all the way down that would slide into a .45 COLT cylinder. Only one time did a customer complain that the .380 we sold him was "making their new gun jam up" Of course their pistol was a 9mm. It is amazing how clueless some people are. It is also amazing they do not injure themselves.