Loading 45 Colt for about 15 years, only one bullet ever gave consistently small groups for me in different revolvers, very soft lead swaged 255 grain, 0,455 diameter bullet that Remington has made forever.
The soft lead 255 grainer worked very well through throats from 0,452 to 0,454 and bores from 0,451 to 0,454. Just about any powder in amounts giving standard velocities (600 to 900 fps) gave respectable to excellent groups with this bullet. I quit buying all other 45 caliber bullets for revolvers.
I suspect that excessive splitting of 45 Colt cases is partly, even heavily, related to chamber sizes, which can be very generous on 45 Colts. Each revolver I used had very consistent chamber diameters, smallest on a R&D 45 Colt conversion cylinder and largest on Ruger -- and range brass was often even larger. Brass was trashed when it became too work hardened (happened quickly) or when it split, and lots split, especially after 5 or more loadings. I attributed rapid work hardening to generous chamber diameters in all but the R&D conversion cylinder -- my resizing dies just barely sized the brass small enough to drop into the R&D cylinder.
I too got rid of all my 45 Colts, and now mostly shoot a 44-40 Ruger and various 357s. 45 Colt was the least satisfying cartridge to load, over about 50 years of reloads, including 32-20 and 44-40, both often considered a pain to reload.
Niklas