The load data I'm basing this off of is:
Starting Hodgdon HS-6/ Sierra FMJ/ Overall Length
6.4 grains/ 125 grn/ 1.090"
The boolit I'm using is Lee's 356-125-2r. Lube is 50-50 beeswax deer tallow with blue crayons for color.
I started with the starting powder dose, and seated for an OAL of 1.115". Plus the Sierra 125 grain FMJ is longer than the Lee boolit, 0.575" and 0.565" respectively.
So I've got several things going for me that would indicate that this load should not have any overpressure problems: Using cast in lieu of jacketed, using the starting load, using a shorter boolit, and a longer OAL (both translating to shallower seating depth).
So I fired off a few magazines not thinking to check right away. When I gathered the brass, all the primers had the dents flattened out. Not cratered, but it almost looked like the primer was unfired - the dimple was pushed back out and flat.
Same load worked without difficulty in my brother's Ruger P-95.