At the transision from black to smokeless, Medford rifling was found to not hold up well to the extremly hot gases and erosive nature of the then new cordite powder.
Today the best way to treat an old rifle gently is to use a cast bullet propelled to a moderate velocity using a modern smokeless powder.
A 220 grain .303 bullet cast from an alloy of 50% wheel weights +2% tin and 50% pure lead driven to 1950 fps with 39 grains of H4350 will take deer very effectively and not wear out your bore.