If one uses a .40 cal mag in a 9mm pistol, exactly what law is being violated? And if the law is being violated, and the ATF are aware of this, as I'm sure they are, why have they not made a ruling or required that the guns or magazines be modified to prevent this illegal practice? Is that 10 round .40 cal magazine that holds 12 or 14 rounds of 9mm considered a high capacity ammunition feeding device? What gives? Have ATF ruled on this?