Do they work? I used to have a P99 9mm (traded it for a P5C) but never got around to trying it. Instead I went out & spent $200 on a couple 16rd mags. I have since found out that a lot of .40 mags will hold more rounds in 9mm with no problems. It's technically legal because the mag isn't modified & will work in the original gun. Since it was a 10 rounder, it also wasn't marked LEO only. How many rounds of 9mm will the .40 mag hold & is it reliable? I just wanted to see if anyone has tried it. Doubt I'll get another P99 unless they make a .45 model.