|Dillon Precision case gauge|
At the time I was not checking every completed round with my case gauge to insure there were no bulges or imperfections on the brass that would keep the round from sliding in and out of the chamber freely. I was checking maybe two of every hundred. Really stupid. Each piece of brass is different. If the brass doesn't fit in the case gauge, it may indeed get seated in the chamber just fine because the slide will strip it off the top of the magazine and force it in. But once in the chamber and fired, the empty case may be wedged in so tight that the force of the recoil is not enough to insure its extraction. In fact, in the case of "death jams," tugging hard at the slide afterwards is often not enough force to extract the round.