One thing you need to be aware of that the MEC single stage presses all produce a lot of variation in the thrown charge weight. It's because MEC parks the powder bushing under the powder bottle while you are stroking that press for the De-Prime/Size, for the powder insertion, and the pre-crimp and the crimp. All that action means that additional powder will get packed into the bushing by the vibration for those strokes and it will vary with each shell depending on the vibration produced. For example a stick primer can add an addition full grain of powder to that particular shell. For a powder like Unique, Clays, or Longshot the Standard Deviation for thrown charges is a whopping 0.42 grains so the 6 sigma range is +/- 1.26 grains.
Note, there is a fix for this issue. One the Sizemaster and 600 series presses there is a black stamped part mounted to the charge bar that MEC calls the Prochek. All you have to do is notch the Procheck so that it will allow the charge bar to be shifted to the left by one bushing diameter. Then while operating the press after dropping the shot charge, which also fills the powder bushing, you shift the charge bar to the left as soon as the press is at it's upward position. This results in the powder charge being isolated form vibration during all those following stages. It also takes the SD from 0.42 grains to 0.17 grains with the above listed powders. Take a look at the images below and look closely at the Prochek and it's new notch that allows a new Park position for the powder charge. Then look at the modification between original and modified.
I've stopped counting.
