Modern muzzle-loaders are pretty amazing. Anything within 150 yards is a gimme shot if you are a good marksman. After that the wind and distance have a huge affect on the bullet. If the deer was standing still on a calm day I might shoot a couple hundred yards. After that you need to be very accurate on distance and wind. The farther you get out the more accurate you need to be. 400 yards is probably very realistic for range shooting on a stationary target, but not for hunting. I am sure some will disagree but I would say 200 yards is about as far as you would want to go without jeopardizing a clean kill on the animal.
