CraigC
Sixgun Nut
I think it's wiser still to just become an informed consumer. I thoroughly every gun before I buy it, new or used are all treated the same. I have bought very few turds but have handled plenty.
I've bought several used Rugers that still had bits of casting media in the recesses of the receivers. This stuff would start flaking off and dropping into the mechanism, causing grinding, binding, and general malfunctioning.
I'd get these "lemons" cheap, give them a dental pick/Hoppe's #9 massage, and go shooting.
My experience is that you MUST inspect the interior of the receiver of any Ruger before use.