I just punched out fifty pistol primers from some 7-08 brass day before yesterday. I have only one tray of pistol primers to my name. After a recent bench cleaning and rearranging, it ended up with the rifle primers. (Winchester large rifle and CCI large pistol primers use slip covers that are very close to the same color.)
I don't know what clued me, but after charging about half the cases in a block of 50 with powder, I had the feeling that something wasn't right. I pulled down the tray from which I had taken the primers and, sure enough, half of them were gone. I am fortunate to have discovered my error while there was still time to straighten things out.
We all make mistakes. Chalk it up to a valuable learning experience--I did.
