Was using my RCBS powder thrower (at least 35 years old) tonight and something happened that has never happened before. I had it set to drop 46.5 grains of H380. I checked and rechecked my weight with my scale, then dropped ten loads seated the bullets, and rechecked again. The second check tested heavy. I tinkered with the scale until it balanced at 48.0 grains. I threw a few more and they all weighed 48 even.
Should have rechecked the weight before seating the first ten bullets. Never expected an error because I've never had it move before tonight.
That's why we recheck and that's why they put a lock ring on the adjustment piece - which I hadn't tightened. Should have known better. Only been doing this for 40 years.