Very nice shooting...for the .45 ACP cylinder to do that well at 25 yards...you have a winner.
My guess for the .45 Colt is that you used the same bullet that you used for the .45 ACP loads. If there is not a crimping groove in that bullet my guess is that there was not enough crimp on the bullet and it caused inconsistent ignition or if the bullet was roll crimped the deformation caused the inaccuracy.
I think you are on the right train of thought about buying a heavier 240-300 grain bullet and running it about a grand...
As to the grips...the last Ruger SA I bought was a Flat Top .41 with the smaller XR3 gripframe...had those grips and was miscible to shoot...
Bob
