VV makes some awesome powders, but sometimes they're hard to find locally.

There is an article out there (Taffin I think), about using 255gr SWC hardcasts with Unique (5.0-6.0gr) to get around 1000 fps from a 5" barrel.

I do know with what I've messed with in the .45 ACP, that 7.0gr of Power Pistol will also give around 1000 fps with a 250/255gr in a 5" barrel.

You could go heavier still, Hunters Supply makes a super nice 275gr hardcast with the perfect profile for the ACP as it can be seated to full OAL leaving a good amount of room for powder. I would say that surely 900 fps could be attained from a 5" .45 ACP.