Thanks, I am only considering it because I can find no powders locally that are good for 9mm and I no longer shoot magnum loads. I have not exhausted the internet but Midway and a few other sources are all out of stock with no backorder taken on the other powders I would use.
Back in 1998 Alliant did not show 2400 powder for the 9 mm but
did had Blue Dot data, so your 2400 powder might be doable in loads
but it was not the best choice, per the Alliant company.
If you have no other choice, I will tell you that my Blue Dot loads did best with the 115 & 124 gr. Gold Dot bullets in my C9 3.5" pistol with a OAL of 1.12", that offered more case volume , than a "Ball" bullet design.
The main problem with extra slow powders is the case volume room that is at hand when a bullet is seated.
Even the old stand by Unique powder, will have problems finding FPS, when you seat a 124 JHP with a OAL of 1.075" !!
2400 powder should work for light target loads and even a standard load if you get lucky, with a long OAL.
Maybe a 7.5 gr load with a 115/124 JHP for starters, to see if it has enough energy to work the slide........?
Hopefully, you can find some data on this idea.
Stay safe.