I’ve shot many many many hundreds of rounds of 45 Colt loaded lightly with cast and FMJ bullets that were originally intended for my 45 ACP. I never had any functionality or accuracy issues in my Blackhawk convertible or Bisley or Model 25, but then again I never stopped firing midstring to look for bullet pull. If the bullets were pulling under recoil, it was not sufficient to either cause differences in power/accuracy or to functionally tie up the gun.
The bullets all got a heavy crimp, using the same crimp die set up as I used for traditional 45 Colt bullets. The cast bullets (MBC IDP#4) were already sized to .452 and had a groove suitable for crimping just south of the natural shoulder. For the FMJ, as was commented in an earlier post, I seated the bullets deeply enough for the crimp to occur just forward of the start of the ogive.
My key thoughts at the time were to keep the loads light, and to make sure I had adequate resistance to bullet pull. Maybe I got lucky, but this all seem to work just fine for me.