+1 to that ! And it was for cleaning range pickup 5.56 cases that I bought the pins, too!
Are there ribs inside that PVC tube drum? I'm assume yes, since there wouldn't be much turnover of there were not. I'm going to try again - my first try using my old 2# Thumlers was a disaster. (The drum isn't watertight. - 'nuff said!) Making a new drum of PVC might salvage the money I laid out for the pins. My drum will have to be bigger than 6" diameter though.
Speed of drying makes no difference to spotting - it's the volume of water that evaporates, and the hardness, that make the difference. I also have very hard water, but I deal with it by dumping the cases on a towel and tumbling them about with another towel to get surface water off. No spots, although I do see a white residue in the primer pockets sometimes. I ignore it.