Ruger has been very smart with their factory mags. They have incorporated a vast network of witches, goblins, and other such creatures to...
#1) put good mojo on their factory mags, and
#2) put bad mojo on everyone elses.
Seriously I've never had much luck with aftermarket mags for any of the Rugers I've owned, so I just bite the bullet and buy Ruger mags.