When I took my first safety course relating to semi-autos, it was pounded into our heads, magazine out first, clear the round from the chamber next.
A guy here in Idaho found out the hard way at a party a few years ago. Got drunk (a "here-hold-muh-beer" thing) was playing with his new "toy". Put the clip in and pulled the trigger - nothing. Pulled the clip out and pulled the trigger - nothing. Put the clip in, chambered a round, safety on, pulled at the trigger - nothing. Pulled the clip out, safety on, pulled at the trigger, nothing. Put the clip in, took the safety off, pulled the trigger (remember the still-chambered round???)- bang. All this time, he pointed the gun at his head at each trigger pull. The round killed him, killed the moron still in the room sitting next to him and went throught the mouth of the second moron still in the room with this drunk idiot.
Talk about a bummer at a party, brains all over the coke mirror.
Don't know if I was on that thread, but count me in that camp. It sounds like something I might have posted.
For the convenience of all, as a public service reminder, I point out
THERE ARE ONLY FOUR RULES!!
Jeff Cooper's Rules of Gun Safety
RULE I: ALL GUNS ARE ALWAYS LOADED
RULE II: NEVER LET THE MUZZLE COVER ANYTHING YOU ARE NOT WILLING TO DESTROY
RULE III: KEEP YOUR FINGER OFF THE TRIGGER UNTIL YOUR SIGHTS ARE ON THE TARGET
RULE IV: BE SURE OF YOUR TARGET
Hit link at top for detail on the four.
Poor training and inept operation is the reason for these negligent discharges. The Glock is a fine piece of hardware. Someone on the thread made a statement about "complicated to clear" or some such. Dogsqueeze. Remove magazine, rack the slide open, ensure the weapon is clear, release slide. The weapon is unloaded until you put it down, at which point you again assume it is loaded. This is not complicated for anyone who can graduate from the 6th grade.
I have read of at least one legitimate accidental, not negligent, discharge, and this was due to a manufacturing defect. I believe this was on a Smith and Wesson semi, and the decocking mechanism was faulty. When the shooter decocked the gun (safely pointed downrange), it fired! The gun store owner didn't believe it was physically possible, until he tried it too. Yup, it fired on decock. Every time.