Thanks.
(no squib yet)

Reading posts like this reinforces to me how critical sequence and cadence are, and NO interruptions. I don't allow myself to goof with or adjust anything while I'm reloading; rhythm is king. It also helps to place the finished loads in a 50-round plastic rack that come in the factory boxes, salvaged from the trash at the range. Plus my Lyman 1200 has a round counter, which I check against the loaded rack on every round. I use my Dillon 450 semi-progressively, so this works for me. I also take a break after every 50 rounds.

Though I do all these things, I still had the nagging suspicion that I'd done something wrong not long ago, so I weighed the whole 100 rounds, pulled the 3 lightest and 3 heaviest and whacked them apart with the kinetic puller, then weighed the powder in each one. They were all fine- but not because I was confident that I could tell by weighing them, as was posted a couple times above.