I was raised by a cop on gun rules and know them front to back. But accidents will happen........
I had a friend and his nephew (the gun expert) over to evaluate my collection. I automatically pulled back the slide on one semi-auto to inspect for any rounds in the barrel, seeing it empty, I let it go then ejected the magazine before handing the gun to my friend.
Fortunately my friend instinctively pulled the slide back to inspect for any round in the chamber and guess what, there was one there. When I released the slide it automatically injected a round into the chamber prior to me removing the magazine........The magazine should have been removed first!!!
I still shudder whenever I think of that moment.......
Don't you hate when that happens?
I recommend that you make it a habit to lock the slide back as well before handing off a gun. If it's a revolver, you can leave the cylinder open.
I have a small semi-auto that not only doesn't have a slide lock, but which locks the slide closed when the magazine is removed. One basically has to have an empty magazine handy in order to properly unload the thing.