Height of trajectory above line of sight if sighted in at X yards. For sights 1,6 inch above bore. The goal was to make a light deer rifle which would still have the advantages of the high-velocity. In Winchester made it a commercial round.
WARNING: Discharging firearms in poorly ventilated areas, cleaning firearms, or handling ammunition may result in exposure to lead and other substances known to the State of California to cause birth defects, reproductive harm, and other serious physical injury. Have adequate ventilation at all times. Wash hands thoroughly after exposure.