Old topic, but i find it interesting that this is one of the hottest debated topics on gun forums, yet when i was looking a few years ago, and again a few months ago, you still can't find very many straight answers.
I shoot only hard cast lead bullets. I was faced with the reality that i was going to either have to shoot plated/jacketed bullets at a gssf match and use the factory barrel, or get to the bottom of whether or not you can shoot lead out of a factory barrel.
I went out and shot 400 rounds out of 2 different 34s, 10 rounds at a time, each time disassembling and checking the barrels. My own experience was that factory barrels lead faster than my KKM barrels, or my xdm factory barrels, or my 1911 barrel. I also found that the lead came right out of one of the barrels, while i had to really scrub the other.
There is potential truth to the kaboom stories, but it seems easy to avoid. And that is by cleaning your barrel every 300 rounds or so.
I have since shot hundreds of rounds out of g26, g17, and g34 barrels. They never get scarily leaded, but i do get paranoid and check on them around the 200 round mark.
Every glock is different. Be careful, and pay attention to the signs.