Re: Pistol Range
It was the thousand inch (27 yard) range used for M1 rifles where there was not enough range area for a full range or for initial training before firing at longer distances. The short range also had the advantage that the shooter could see the bullet holes.
Due to the trajectory of the .30 Ball, a rifle sighted in at 27 yards would be on target again at 100 yards. The short range zero caught the bullet as it was rising above the line of sight, at the longer range it would be on the way down.