cowboyjared
If you are referring to the minimal 'mouse fart' loads some shoot even in a .45 Colt, you're right - it might not be a viable deer rifle.
However, if you use any of the many 1000 fps+ 250 gr .45 Colt pistol loads in all the loading manuals, you're good to go. With the x-sectional diameter of a .45 bullet, won't matter if it's SWC, RN or RNFP, whatever shoots best.
A pal neck shot a deer at 200 yds with his .45 Colt carbine. He admits it was a 'scratch shot', but it dropped like it had been hit by lightning. He figured he'd hit it or it would be a clean miss. Load was his .45 Colt CAS load with 250 gr bullets.
Of course, you can do what our pioneer forefathers did without any worries - shoot a 250 gr BP load. Worked then and no reason for it not to work today.