This is a tool to sort 380 from 9 mm cases. Simply put the two pieces together with an m4 bolt (it's a 5 mm hole) and dump brass onto the top. The brass will fall into the holes and stand upright. Remove the top portion and look across the top to see any height differences. The shorter ones are the 380 to be removed.
I just used Tinkercad for this and my slider to modify a 45 ACP ammo box. 9 mm ammo boxes were too small and 40 S&W was also too small for the cases to fall in easily.
https://www.thingiverse.com/thing:5249323
Any feedback is appreciated.