Well if you have your heart set on getting and using a .45 Colt then I suggest you wait for a perfect shot opportunity. Broadside and standing still and aim for the heart lung area behind the shoulder. Don't hit the shoulder or you'll likely end up just crippling the deer and not recovering it. Factory .45s are capable of killing a deer but they aren't loaded to the rifle's full potential as they are factory loaded to be safe in all firearms chambered in that cartridge.