Just picked up a Super 14 for the Contender before Christmas. Topped it with a TC 2.5X7 scope and testing with factory Winchester 45GR Varmint loads, 40 rounds for $12 @ Walmart gives me 1" groups @ 100yds. It was stated here that the heavier, longer .22 cal. bullets might not stabilize at pistol velocities. I have not tried anything heavier yet.
The Super 14" barrels are the shortest that I have, so can not speak to the usefulness of a 12", but expect that it would be fine.
Good Luck, Rol