In the past I woud have recommended Penn Bullet, or Russell, a local caster.
Now I am using diamond hard bullets and they are actually a bit softer than either of the above. Penn bullets are brinell 21, and Russell are brinell 18, the diamond hards are like 14, much softer.
I have been using trailboss powder 5.0 grains with a 200 LSWC, I am getting excellent accuracy and no leading.
The thing that I found is that if you are using harder bullets you have to drive them at a higher velocity to avoid leading, Harder bullets may if driven too slowly fail to obdurate or seal to the bore, they then suffer flame cutting which will cause leading. So its imortant to match the Hardness to the velocity. Brinell 14 bullets lead the least at 800-850 fps, I have found this to be true with Unique, Bullseye, Clays, Titegroup, solo 1000 (current favorite of bullseye competitors at my club) and Trailboss powders in .45 acp.
I load and shoot this bullet, 200 lswc by the thousands every year, and trailboss is the best powder bar none, no smoke, no leading, unbelievable accuracy. I have shot the smallest groups with this powder out of my, 1911s, model 625, and model 22 and blackhawk revolvers.
I have also loaded a couple thousand Berrys plated bullets the drawback with them is you have to load them a little longer for 1911s than the Blackhawk likes so I have to keep two seperate batches.