Recently I reloaded mixed headstamp 40 S&W's. Starting to shoot them up, I had a squib. Could it have been me? Nah, it must have been Lee. Anyway, I didn't want to tear the whole batch apart to check for other squibs, so I laboriously measured samplings of case weights for each headstamp, calculated the maximun and the minimum they could weigh properly loaded, and found that for each headstamp a missing charge weighed more than the max-min difference. In other words, a squib case should always weigh less than the lightest properly loaded case. This also accounted for bullet weight variations and powder throw variations. Found a few that were marginal, shot them up with no problems, and moved on. So, from now on, no mixed headstamps to make it easier to weigh for squibs if necessary. Headstamp sorting is a pain, but a bit like laughing at state plates on a trip of places you wouldn't want to live, you get to see some interesting range brass you might want to discriminate against in reloading.