The factory level of loads for the 45 colt IMHO are on the light side for big game hunting. Of coarse they will work from the practiced hunter, but they are not ideal. I once loaded up 10Gr's of Unique and a 250HP for my little sisters first deer rifle. She never did seal the deal and shoot one with that load. Its an old Keith load, supposedly safe in Colts.......
Ruger/Contender loads on the other hand, work very well with in the range limitations of say 125 or so yards. The bullets just loose steam fast and ballistically are not built for longer ranges.
If I had to choose a favorite, I'd choose the 300Gr Speer SP, (Your 270 Keith, hard cast would qualify) in front of a stiff load of H110/W296 and a CCI 350 primer. Using this load I have seen two different deer shot thru end to end. One running away, aka Texas heart shot and the other facing. That bullet and load has also accounted for some two doz or so others. A couple bang flops, all recovered in short distances.
At one time this was my favorite for NE deer hunting. It's still a second choice, now my 357Maxi is #1 choice. I have a number of small plots of private land in well populated areas to hunt. I just don't feel right shooting "big guns" (358, 30-30, 375Win) there. Dont get me wrong, I'm talking 30+ acre pieces for the smallest. But people are with in earshot and the lower noise levers keep me on speaking terms.
Find a heavy .45 bullet and load your gun likes, put the bullets where you know you should and don't worry, the Ole' colt will not let you down.
CW