Originally Posted by mtgianni

Extrapolation is necessary when you have a wildcat [cartridge A] with a similar bore and case capacity to another [cartridge B]. If I have a 6.5 bore case with a 46 gr water capacity, I can compare it to a .257" bore and a case with 44 gr water capacity and a 7mm bore, 44 gr water capacity to see what start loads run between bullets of similar weight and length. I know that my wildcat [cartridge A] will never be listed in a loading manual, but can extrapolate starting loads from the other two to arrive at a start point. I cannot safely extrapolate maximum loads but a chronograph will let me know as I approach targeted velocity.