A little advice about 40 Compact mags many seem to have forgotten.

[threefeathers]

The 10 round mag in 40 or 357 Sig will hold 12 rounds of 9mm and will function perfectly. It was a way to get high caps legally during the AWB.
So if you want to stock up on cheap High Caps and you have a 9mm got the 10 dollar 40 Compact mags now.
I got 10 of them so my 9mm P2K has 15 high caps ready to go.

[rkwallace]

Is this true for full-size mags also?

[UrbanKnight]

Yes...

Was also very popular with the XD line from SA too...