I suspect that MartinS is right, and I would be very suprised if it left Ruger with a .003" barrel/cylinder gap. Usually they are .006" - .010".
I will assume that the cylinder face is flat and true (although it might be that it isn't). If this is the case and the revolver was returned to Ruger I suspect they would use a cutter with a pilot (to keep the cut square) to trim about .003" off of the back of the barrel. This could be done with a file, but the cut might be angled, and that wouldn't be good.
At this point I would call Ruger's Customer Service and see what they might say.
1-928-541-8820 (Toll-free I think).
I will assume that the cylinder face is flat and true (although it might be that it isn't). If this is the case and the revolver was returned to Ruger I suspect they would use a cutter with a pilot (to keep the cut square) to trim about .003" off of the back of the barrel. This could be done with a file, but the cut might be angled, and that wouldn't be good.
At this point I would call Ruger's Customer Service and see what they might say.
1-928-541-8820 (Toll-free I think).