round

今日の単語も "JFK The Smoking Gun" の記事からです。
A quirky characteristic of the early-model Colt AR-15, the model of AR-15 in use by the Secret Service in 1963, is the rifle was prone to smoking; that is, due to its direct gas operating system, it would emit excessive levels of smoke each time a round was fired.
この "round" はこの後にももう一度次ぎのように出てきます。
All this could prove key evidence in tracing a suspect and assist the FBI on the vital information of what type of round was responsible for the devastating head shot to JFK.
こうなると "round" は弾丸の事だとほぼ確信できますが、辞書で確認します。
・Collins Dictionary: a single discharge by a number of guns or a single gun: a bullet, blank cartridge, or other charge of ammunition
・Cambridge English Dictionary: a bullet or other single piece of ammunition: The soldiers had only 20 rounds left