Caldwell Ballistic Precision Chronograph The Ballistic Precision Chronograph provides accurate velocity measurements across a wide range of shooting conditions. Higher accuracy was achieved by using a high speed 48 MHz processor and by designing a circuit with an advanced data interface that allows each unit to be computer calibrated at the factory after assembly. This unit is designed to be simple to operate, displaying velocity in Feet per second or Meters per second on the large built in LCD screen. The Chrono can also deliver the shot string velocity data through the 15' foot audio jack cable (included) to an iPhone or iPad. A free App is available for download that displays the velocity of each shot on the phone screen and records it with other data identifying the load and environmental conditions.