I saw in Hodgdon load data (on their website), starting loads for .357 Magnum, Lil' Gun, 158 gr. Hornady XTP are 16.0 grains, and velocity with 10" test barrel is 1504 fps.
In Barnes data (on their website) for 140 gr. XPB, the maximum load of Lil' Gun is only 15.0 grains and velocity is 1669 fps in a 10" test barrel.
So what I'm concerned about here is Barnes says 15.0 is max load for a 140 gr. bullet where Hodgdon is saying to start at 16.0 grains for 158 gr. bullet.
The two things I can think of that could be different are the start pressure and the bullet length. Both data sources specify OAL of 1.580", but the solid-copper 140 gr. XPB is slightly longer than the lead-core 158 gr. XTP. Theoretically, the start pressure of a solid copper bullet should be higher also, but in Quickload both bullets are specified with the same start pressure. I imagine a real difference in start pressure starts to matter with thin-plated or soft-cast bullets. So it must just be the length of the bullet. Using Quickload, there can be seen big differences in pressure with seating depth, but primarily with short cases (and not in Quickload but with rifles due to seating on the lands). In long cases in a revolver, there should be less sensitivity to small changes in seating depth. Besides that, it seems the listed pressures are low (Hodgdon's maximum is only 25,800 CUP). So maybe it just has to do with how much the Lil'Gun will be compressed.
In Barnes data (on their website) for 140 gr. XPB, the maximum load of Lil' Gun is only 15.0 grains and velocity is 1669 fps in a 10" test barrel.
So what I'm concerned about here is Barnes says 15.0 is max load for a 140 gr. bullet where Hodgdon is saying to start at 16.0 grains for 158 gr. bullet.
The two things I can think of that could be different are the start pressure and the bullet length. Both data sources specify OAL of 1.580", but the solid-copper 140 gr. XPB is slightly longer than the lead-core 158 gr. XTP. Theoretically, the start pressure of a solid copper bullet should be higher also, but in Quickload both bullets are specified with the same start pressure. I imagine a real difference in start pressure starts to matter with thin-plated or soft-cast bullets. So it must just be the length of the bullet. Using Quickload, there can be seen big differences in pressure with seating depth, but primarily with short cases (and not in Quickload but with rifles due to seating on the lands). In long cases in a revolver, there should be less sensitivity to small changes in seating depth. Besides that, it seems the listed pressures are low (Hodgdon's maximum is only 25,800 CUP). So maybe it just has to do with how much the Lil'Gun will be compressed.
