Jim- You need ammo that is marked either .44 Remington Magnum (or just .44 Magnum) or .44 Special. The magnum is the more powerful round. Don't use any other .44 marked ammo such as the .44-40.
There is a huge ammo shortage right now especially in handgun calibers so it may take you a while to find any especially at anything resembling a reasonable price. Please be very careful, you have a powerful weapon that can bite you if you not used to the recoil.
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Jim
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