Note Please: the SAMMI Pressure for 9mm+P 38,500, case volume 0.86 ml and for 357 SIG it's 40,000 & 1.26ml = ∆ +42% increase in case volume
Just from the Hodgdons data for a 115gr Nosler jhp in 9mm+P vs. the same bullet in 357 SIG some "food for thought", hopefully...?
9mm+P MAX 6.2gr TRUE BLUE 1190fps @ 38,300
357 SIG START 8.2gr TRUE BLUE 1217fps @ 31.900
357 SIG MAX 9.1gr TRUE BLUE. 1352fps @ 35,400
TRUE BLUE is a very fine grained powder and you can get quite a bit into these cases: a 9mm case.will easily take a LEE #0.5 dipper of 7.2gr with room for the Nosler 115gr jhp without compressing the powder & the LEE #0.7 dipper is 10.2gr in the 357 SIG case with room to spare.
Someone with QUICKLOAD can probably estimate the pressure and projected velocity for a 9mm+P load with an "extra"(?) 1g of TRUE BLUE, but I guarantee the pressure will be well over the +P SAMMI maximum.
On the other hand a 2gr increase in the 357 SIG load would fit and what the projected pressure and velocity would be might not actually exceed the SAMMI maximum: there's quite a bit of room between 35,400 and 40K. Here QUICKLOAD info would also be much appreciated.
This has indicated to me that one gets quite a bit of performance in 9mm+P with this bullet and this "by-the-book" powder combination, but there seems to be a sig(pun?)nificantly greater load development window of opportunity for further load development in 357 SIG.
Any thought or comments would be appreciated.
Cheers!