The thing to concentrate on is the handgun, if you decide you like the caliber. Once the caliber is chosen you must check the individual revolver to determine whether or not you want it! If it's crap then who cares what caliber it is?
Is the muzzle crown good, is the action smooth, is the timing of the cylinder lock-up good ahead of the hammer falling, is the grip frame tight to the cylinder frame. Is the barrel pitted. What is the barrel to cylinder clearance and what is the cylinder end-play. Are the hammer and trigger properly mated for sear engagement -- if you know how to tell this on a Ruger from looking at the two parts with the hammer cocked. If the hammer is cocked and it is pushed forward with significant thumb pressure will the engagement hold..... What condition are the front and rear sights in.....
These are the things you now look at, if the caliber is OK.
If the timing, barrel-cylinder gap, cylinder end-play, or sear engagement are improper then forget the revolver. It's not worth buying a used weapon just to pay for it to be fixed.
Sorry, but there's too much to look at with a used piece besides caliber.
Take care.