I've had one and luckily I recognized it from both the lack of recoil, or sound. It happen while I was checking out a friends CZ 9mm on his property, so it was pretty easy to notice, not to mention it was so weak it didn't even have enough energy to operate the slide and strip off another round. It must have been one of the weakest squib loads ever, I was able to use a pencil to back it outa the barrel and fire off a few more rounds. I do recall being nervous while using ammo from the same ammo case, but that was all he had. No double taps that day.