Depends on how good you can shoot it
. Seriously, with good bullets a .44 mag can take deer out to 80 or 100 yards. However, most people can't shoot well enough at 100 yards with a revolver to consistently take deer, especially with open sights. I know I can't shoot that well. You should practice and see how far out you can consistenly hit an 8" circle. An 8" circle will give you a good idea how far out you can consistently hit a deer in the vitals. Most people with some practice can do well out to 50 yards, some people may be able to hit out to 100, especially if you have a scope.