This is the “Powder Mag”
My first attempt at a fast, consistent, and precise powder dropper for reloading.
Has been working well with ball and extruded powders, I have not tried flake powders.

With the few powders I have tested, it has an accuracy spread of about 0.05~ grains for ball powders, and 0.30~ for extruded powders. 

The numbers on each slider denote the hole's diameter in millimeters (not grain count). You will need to document your own grain count for different powders. 
Note: The powder needs to settle, so the first 1-3 drops will be wild.

I print the sliders with 10% infill. (no supports needed)
I print the mag with 20% infill.

I use build-plate tree supports as show in the slicer photo.
I only support the area where the sliders contact the mag, I block supports anywhere else (block supports for the shelf inside the hopper). 

This kit has a break-in. The sliders will drag in the mag when first printed, but will smooth out and slide freely after a short amount of time.