If either the primer or secondary ignition ignited all granules before the bullet had moved significantly into the bore,QuickLOAD prediction bias should equal. Independent QuickLOAD results show no bias within the propellant descriptions, or with any other factor, that might explain this dramatic difference in predictive accuracy.
The following table compares these two numbers with various nominal loads. I chose these numbers because this pair shares an extremely similar propellant column shape. A comparison between the 308 Winchester and the 45-70 shows a similar result.
458 Winchester Magnum (500 H
RN)
7mm Remington Magnum (175 H SP)
A comparison between the 308 Winchester and the 45-70 shows a similar result. Again, I chose these numbers because this pair shares a similar propellant column shape.