The most obvious answer here is one I have run into more than a few times with 357 Mag. We all know there are two pressure measuring systems, PSI and the older Copper Units (CUP) system. With these two systems applied to 357 there is quite a difference in the two limits. 35,000 PSI on the newer true PSI system and 45,000 CUP on the old. You can’t always make this statement because the systems vary from cartridge to cartridge and there is no real mathematical formula to convert from one system to the other. But in 357 Mag one thing that can be said for sure is when the CUP pressure system and limits are used in the testing, the result is much stronger/hotter/powerful loads. You can even see it across the load data that Accurate themselves have published over the years as they started with 357 in PSI, then for a few years used the CUP limit since other powder manufacturers powders/loads showed greater performance (using the CUP system) they switch their 357 loads to CUP testing. Now they are back to PSI and the lower load limits.

Mark in GA