Do check and make sure that old guy REALLY IS 3". Anything is possible in old guns since in those days the customer always was right, but I suspect that it was designed for 2 5/8" or 2 1/2" shells originally and any longer chamber was done aftermarket.

No reason to strain a gun that is pretty uncommon to begin with and in a rarish rifle chambering. Be neat if you could pass it along to the next generation, used, loved, and still sound! American made drillings in interesting chamberings and with family history are not found in every pawn shop....more like winning the lotto!