If a Ruger Blackhawk is used, there's negligible difference from a .44 Mag. Bullets of 250 to 300 grains are available.
Regardless of bullet weight, it is common that the more effective bullet is one with a large meplat. And, as noted above, the range is limited mostly by pressure level. A .45ACP is more limited than, say, a .44 Mag.
I've always believed that an outer limit for a handgun, particularly one with open sights, is that distance at which you can reliably hit the end of a beer/soda can.
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