McCary was the son of William Nabors McCary and the former Nell M. Moore. He worked as a ranch hand on Shades Mountain and graduated from the Shades Cahaba High School before joining the Navy. He played tuba for the U.S. Navy Band No. 22 under Frederick Kinney, which was assembled at the Navy School of Music in May 1941. McCary was nicknamed "Swede" as a member of the ensemble.
The band reported to the Arizona on June 17 of that year. When the air raid sirens sounded on December 7, band members reported to battle stations in the ammunition hold below deck. All members were lost when the magazine exploded under fire. The Navy's band competition trophy was renamed the "Arizona Trophy" in their memory.
- At 'Em Arizona (July 8, 1941)
- William McCary at navy.togetherweserved.com