I would consider the 454 Casull. It is extremely versatile and can be loaded as follows

45 Long Colt 250 to 400 lbs/KE
45 Long Colt +P 750 to 1200 lbs/KE
454 Casull 1600 to 2000 lbs/KE

The 45 Long Colt +P is about the same ballistically as a 44 mag but many feel it is more tame to shoot. That would be plenty to take on deer sized game. It also gives you the flexibility to shoot regular long colts at the range and step up to 454 if ever needed for larger game.