DAA Magnetic Powder Check
This is a great idea, very easy to set up. I believe they are 'almost' there, but not quite. The problem is the plunger (I have only tested the pistol plunger) has a tendency to catch on the push rod. It binds as the rod is raised, so even if there is no shell in the holder, it lifts the plunger to make contact with the switch and gives a false reading. It is random, doesnt happen every time. I think they need to make the guide hole in the plunger 1-2mm larger.