I ran a batch of Xtreme 240 gr. plated flat round nose with 7.0 grains of R.D. through my 7.5" SRH. It was a decent plinker round with reasonable offhand accuracy. This was old formula R.D. that I was burning up and was surprised to find that it left the cases fairly clean and not too bad on the grey residue left on the gun. I wouldn't push it too much harder (maybe 1/2 grain) as this is a fast powder and you can jump pressures through the roof real quick with it.
Hercules book from 1992 shows 7.7 grains as max for 240 gr. soft point.