Am I the only one who didn't know that you can load and shoot 19 9mm rounds out of a Mec Gar CZ .40 12 round magazine? It didn't dawn on me to try it until last night. I had purchased a used gun while killing time waiting on my buddy to get off of work. I had only .40s with me for this range trip. The gun I bought was a 9mm and came with only one 10 round mag. Necessity being a mother, etc., etc. Anyway, this effectively doubles my magazines. I suppose it works the other way around too?