I was reading my SPG Primer and ran into something that did not make sense to me. The SPG Primer gives loads for each cartridge with something like 12 grains difference in powder capacity between the two, with the .38-56 able to hold 12 more grains than the .38-55 using the same bullet. Yet Cartridges of the World states there is only 1 grain of difference in powder capacity between the two cases. Which one of these two is correct. Seating depth in a single shot should not be that big of a variable between the two, should it? I could see seating depth making some difference in a lever gun depending on OAL but not in a single shot.
Just a little confused here.