A guy I shoot with has a couple of different Taurus pistols that accept the same mags. The big mags hold more then ten, and stick out the bottom of the grip when inserted in the smaller gun. They do function fine in the smaller gun (sorry, they're not mine and I don't recall model numbers, 45 ACP double stack mags, maybe 24/7 or Millennium Pro?). Kind of like the Ruger SR9C, except the big mag doesn't have the plastic shell on the part that hangs out.
Luckily we're not in CT, but I suspect there are tons of guns by other manufacturers with the same feature. Would these mags, even if blocked to 10 rounds, be illegal if one owned the smaller gun also?
(Just realized that's what the previous post is referring too. Sorry for the dup)