Checking my Hornady and Sierra manuals, a 240 gr JHP is max at 24.2 gr in the Hornady manual, 23.5 gr in the Sierra, with their bullets. You don't mention primer, WLP or other brand magnum is suggested. Currently the IMR4227 is the only available 4227. The Hodgdon website gives a maximum load of 24 gr with the 240 gr Nosler JHP and a Remington 2 1/2 primer. Tapping the case after charging to settle the powder is a good idea before bullet seating.

FMJ, really???

Assuming you get 1700 f/s, 0.8 in high at 25 yards is supposed to put the Sierra JHP dead on at 100 yards.

My personal experience is with handguns, the 2400 has a much louder muzzle blast. Alliant lists 21 gr as the current maximum load. I'd have to find my load notes, but IIRC, I'm using the Remington 240 gr SJHP, 23.5 gr IMR 4227 and a CCI Magnum LP primer. I get 1200 f/s out of a 6 inch revolver.