Originally Posted by
yondering
On my Glocks, the barrel has to be at least halfway locked up to drop the striker. A round has to be fully chambered to allow the barrel to lock up that far. Any round that is slightly oversized, or too long, enough to prevent fully chambering, will also prevent the barrel from locking up in the slide at all, and the gun will not fire.
I'd bet what KYCaster saw was a case of a hot load or a dirty gun unlocking early, rather than firing from an unlocked condition. I've seen evidence of that in 10mm Glocks too.
A really dirty gun is the only way I know of to get the slide to stop back far enough to still fire, but not lock up the barrel completely.