What hardness are you guys running?
I have had great luck with wheel weights powder coated and quenched at about 1150-1200 fps with my 315 grain.

What are you getting good results with in the 255-260 grain bullets?

bout 10 maybe 11.
plain base.

Im pretty sure that's about where I am at with my lead.

Clip on wheel weights are in the ball park of 12 if I remember correctly.

I used the 'original' 45 Colt 250gr bullet cast from Lyman #2 alloy in my 455 Webley MkVI revolver.
The mold was the plain base Lyman #454190 with alloy hardness BHN 15 (according to specs for Lyman's #2).

I loaded to 700fps in the Webley and apart from taking numerous opossums, rabbits and hares I also took several feral goats and a couple of red deer with the Webley and this load as well as one cattle beast with a broken leg, a head shot from about 5m away.

Never recovered any bullets from animals but ones recovered from target shooting into a sand backstop didn't show any expansion. May have done with higher velocities in the 45 Colt although I imagine 12-13 BHN would be more conducive to expansion in the Colt.

I got good accuracy in the Webley with the 454190 bullet.

I been dropping all my bullets from the mold into cold water.

I can not dent them with a finger nail.

Mostly wheel weights some unknown lead and some pure lead just thrown into the pot together.

They do not deform they kill just fine.