Naval Jelly is a BAD idea. Way too agressive.
Try J-B Bore cleaner, as someone mentioned.
You can also try, and don't laugh....
Coke or Pepsi.
They have phosphoric acid in them, which is a pretty effective rust remover. It's in pretty light concentrations, though, so it won't be as agressive (or fast), but at least you won't do any more damage to your bore.
------------------
Smith & Wesson is dead to me.
If you want a Smith & Wesson, buy USED!