Sorry if this is a little off topic but I've survived a couple dummies myself so let us live and learn.
OK confession time. I"ve been shooting guns for 60+ years but made a newbie mistake. I was shooting my pistol collection one day and mistakenly loaded a 1911 45 magazine with 40 S&W. It was hot that day and I took off my sweat covered glasses and picked up a box of ammo without glasses on (very farsighted). Bad move: don't do things you can't see. First shot sounded funny. Second shot stovepiped. I saw the bullets hit so nothing in the barrel. Put my glasses back on and a 40 cal case was jammed in the port. I couldn't find any damage to the gun.
The 40 S & W cartridge should just fall out the muzzle and not be hit with the firing pin. I guess it's like someone once told me: 1911s don't chamber on the case mouth(even too short cases will fire), the cases are held in battery by the extractor.