Like the other folks have suggested, I'd try several different loads. You probably should concentrate on the bullet 1st, velocity 2nd.
For a place to start, I'll pass on my favorite (most accurate) .45 acp load. I use it in all my .45's, including a 625.
200 grain LSWC cast Silver Bullet (fairly hard)
4.5 grains Bullseye
Federal standard primers
I seat the bullet just a couple thousandths short of the SWC sholder, and use a slight roll crimp.