The good news is that it is a drilling not a double rifle. With only one barrel to worry about, you will find a commercial load that will be very close to the factory sight at seventy yards or so. Remember too, that no German would have a drilling in such a caliber without a set of claw mounts and a scope. The open sights were for drive hunts where hare, pheasant, and huns were the primary game, but also where a big boar might also flush. Any shot would be very close and the small pop-up sight was perfect for a quick rifle shot for what was primarily a shotgun hunt. Whenever he would sit for roe deer (or late night posting for boar over bait), he would have a telescopic sight mounted (usually a very good one) and then the shotgun barrels were secondary for fox or a stray cat. J.J. at Champlin Arms does a great job on claw mounts should you ever be so inclined.
