Buy a pound of loose black powder or a container of Pyrodex. I would also go with a patched round ball of soft lead that will give a little better expansion at lower velocities.
Start your load out at about 60 grains of powder. Throw in a couple of 70 grain loads and see if she can tell the difference. If she can, then drop your load back down to 60 grains of BP.
60 grains or 70 grains of BP and a PRB is more than adequate for deer to 50 yards.
In a way I have to agree a bit with Muley. Recoil is part of the game. But a 60 grain load or a 70 grain load with a PRB should not have alot of felt recoil from an MZ.
Certainly the guys are right that a 50 grain load can get the job done. But it is definitley not the optimal load for good clean effective killing of an animal that we owe that to. Tom.