Hey Jeff, I'll take a run at it! It's easy for me to replicate the FOOB event with any of my 3rd Gen Glocks by holding the slide sightly back and pulling the trigger. As the striker falls, the slide moves forward slightly into full battery. If the chamber had been loaded, and the primer sensitive enough, the gun would have fired in the partially OOB position. As you know, if it were not for the recoil spring, the slide would move back OOB on it's own when the trigger is pulled.
The culprit in FOOB seems to be one or more of the following:
Badly fouled chamber, out of spec ammo, weak recoil spring.
I personally ran into this problem with my Glock 21. Best I could determine, the pistol was extremely fouled, and the stock recoil spring had in excess of 12k rds in service. My first clues were failures to fire due to light strikes. I was shooting a course at the time, and just did failure drills to get the gun back up and running. Later when I retrieved my cleared rounds, I noticed the light primer indentions were in the high 12:00 clock position. Fortunately, the strikes were too light to fire the primer, so the pistol did not fire out of battery. Had I been using Federal, with their more sensitive primers, rather than Winchester, the result could have been far worse.
With well maintained pistols and good ammo, I'm not overly concerned, and I continue to run my Glocks. I would only suggest to you, that should you start to get failures to fire from any of the Glocks in your charge, check them out immediately for the telltale 12:00 high light primer strikes. I'm sure that a search would give you a lot more and better information than I did, just wanted to relate my experiences. Stay safe!
Savage