Nassau County police said the man was struck in the left hand by the bullet fired from his .22-caliber magnum bolt-action rifle at about 8:45 p.m.
Police said the man said he was attempting to clear "a malfunction" from the rifle when the round was discharged.
It was not clear where the man was when this happened.
According to its website the range is "the only such facility open to the public in the county." There are six ranges and 30 individual shooting points available, according to the site, and hunting safety classes are also offered. The range is at the Mitchel Field Athletic Complex near Nassau Coliseum.