I have the 4 inch Redhawk 45 Colt, from before they offered it in 45 Colt/45 ACP so I cannot speak to the ACP side. I had the cylinder throats opened up to .4525 by the Cylindersmith before he retired. Prior to that it grouped cast bullets into about 3.5-4 inches at 25 yards. After he honed the throats and I fire lapped the barrel, it stacks them in one tight little 1-1.5 inch group out of a Ransom Rest at 25 yards.

The guns are tanks. They'll take some pretty heavy loads. I shoot 300 grain cast about 1100-1150 fps out of mine which all I really need from it.