Ex 49'er,
Listen to George here. He's right on the money. Mike and I have 1" smoothbores all over the place and even with 1" rifled guns, we still follow this method. Even with fancy bore sighting lasers, we still move the target in close to 30 yards so we can adjust the sights quickly and easily. The trajectory brings the bullet very close to the bullseye at 100 yards upon passing through the the line-of-sight for the second time.
Regards,
Mike and Tracy
Seacoast Artillery Company