RSIno1,
When my dept. went to the Glock 17 back in 1991. All instructor's of course had several days of training by folks from the company. Back than the head guy warned us about ADs. At the time he quoted how many cops in the US had shot themselves. It was not from finger on trigger when holstering so much as improper take down for cleaning. Rookies would remove the mag fine, but fail to clear the chamber. Then pull the trigger. At that point in time he said more Glocks had shot cops while being cleaned than in gun fights. We had to have the New York triggers installed on on Glocks for about 2 years. It was supposed to be similar in pull to a double action revolver. It sucked and really many shooters had problems with accuracy, so the NY triggers went away. We were lucky in the 6 years after that no ADs from fail to clear the chamber before cleaning and none while holstering. Some ADs did happen due to finger on trigger at the range and moving before time to fire. But, happened with revolvers, shotguns and rifles also. After that I was out of the loop and it may have happened.