A little over a month ago I contacted Springfield Armory about hi cap mags since the gun ban died. They hooked me up with a swap for the two mags that came with my Tactical .40 plus I bought a couple more for it. The pre ban were 10 rounds, of course, and the post ban were 12 rounders.
While I was talking to them about that deal I asked them about hi cap mags for my 9mm Sub Compact. They told me that 10 rounders were the only mags they would have available for 9mm Sub. I have heard you can buy some mag extenders from Pearce. I have also heard that you can take .40 cal Sub Compact mags and just load them up with 9mm's and the mag is supposed to fit in the 9mm mag well. You do have to tweak the mag lips in a little bit to position the cartridge properly for feeding.
You can get about 13 or 14 9mm's in a 10 round .40 cal mag
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