RE: Colt Gold Cup .45
Not sure about today's production version, but my Series 70 Gold Cup will in fact digest hardball; there is nothing in the manual saying otherwise. Having said that, the spring is lighter than a Government Model, the slide is lighter, and I have installed a recoil buffer to minimize peening of the slide against the frame. I prefer to shoot light loads in mine; for hardball I've got a Springfield GI 45.
You can always buy heavier springs for these also.