I've got some MEC data sheets that actually differ (as far as powder weight corresponding to the respective bushing) as I bought my first MEC around 1974 and the sheet differs from recent ones. I believe only using the chart as a reference but as Reagan said "Trust but verify". You need to weigh each powder lot and some people even suggest that you weigh the next container even if from the same lot. Powder variations makes or breaks the shell; i.e., variations can result in lost targets, then trusting your reloads amy be an issue. Sometimes, if you're trying to get within 2/10th's of a grain, you may have to hone out a smaller MEC bushing, then mark it so you know the bushing has been adjusted. Just my opinion. Darrell