The Hollow Base allows the bullet to be longer and provides more contact area with the barrel and rifling which will stabilize the bullet and improve accuracy. The bullet profile is longer but the weight of the bullet remains the same and you can load these bullets using any published load data for a jacketed bullet as long as it is the same weight bullet. These bullets are guaranteed to handle velocities up to 1250 feet per second. Berry's recommends a COL of 0.970?