Depends on gravity of the body and its atmospheric pressure and related variables (wind speed, temperature, composition - lead bullet could meld on Venus, etc.)

Depends on gravity of the body and its atmospheric pressure and related variables (wind speed, temperature, composition - lead bullet could meld on Venus, etc.). Low gravity & no atmosphere- bullet reaches escape velocity and wanders off to space. Very high atmosphere & fired high up above ground (if any - eq. gas giant) and bullet might take quite a while to fall.