SAN DIEGO — Chuck Mawhinney, the Camp Pendleton Marine who became the deadliest sniper in the corps’ history while serving in the Vietnam War, died on Monday at his home in Baker City, Oregon. He was 75. The Marine Corps credited Mawhinney with 103 kills as well as 216 “probable” kills that could not be confirmed because of the dangerous conditions in which the shootings happened. Mawhinney, who attended Camp Pendleton’s Scout Sniper School, made the kills during a 16-month period that began in early 1968, when he was fighting the North Vietnamese Army and Viet Cong. He was a member of Camp Pe…