I suppose I am the last to know.

[Birds Away]

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?

[bang bang]

some mags are swappable. you just have to do some homework to figure it out.  sometimes it T&E too.  if the feed lips of the 40 mag arent strong enough, the 9s will pop out.  it will depend on the mag.

[motosapiens]

yep, you were the last to know. I was 2nd to last. the only difference is where the holes are drilled. I bring a 9mm mag as an emergency backup for idpa and uspsa matches. I generally don't use it because i have to empty it and count out 10 rounds each time i top it off. I should probably just drill a 10-round .40 hole in the side.

[jameslovesjammie]

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?

This only works with the AFC magazines.  The standard 12 round Mecgar and CZ factory 12 round magazines have wider feed lips.  9mm will pop out if loaded in these magazines.  The 26 round CZ 9mm round will also feed .40, but the capacity is around 16 rounds.