Did you read the thread?
He didn't pull the trigger, unlocked the slide lock and as he was pulling the slide forward he was cocking the striker against the trigger bar.
Idiotic thing to do anyways - field stripping a loaded gun....
I did read the thread. I have also field stripped a lot of Glocks. If someone can explain to me how it is possible to pull down the slide lock, then pull the slide forward more than a quarter of an inch without PULLING THE TRIGGER, I'm all ears.
Here is his description of events, followed by my translation of what happened:
Racked the slide, held down the slide lock, released the slide forward and in an attempt to keep the slide from falling onto the ground, put it to my left thigh
1) Racked slide, and either did not notice it failing to lock back, or did not notice mag inserted
2) Held down slide lock
3) "
released the slide forward". Commonly known as "pulled the trigger".
4) Pointed it at thigh. This should be listed as step 3, because once you pull the trigger and the gun goes off, pointing at your thigh won't cause you serious problems...it's really the pointing it at your thigh THEN pulling the trigger that's the issue. So clearly he pointed it at his leg, then pulled the trigger.
I might also point out that in post 652, he describes himself as having "flat out pulled the trigger".
I feel there is no realistic conclusion, then, other than that the trigger was pulled, almost certainly by him, and that either he did it while pointing a loaded gun at his thigh, or, conceivably, immediately before pointing a gun at his thigh, and that he then used the subsequent .004 seconds while waiting for the bullet to exit the barrel to point the gun directly at his thigh.
In sum: try to avoid pointing loaded guns at yourself and pulling the trigger; if that is impossible, try to wear armour over the zone you intend to shoot.