空薬莢（やっきょう）を英語でなんと言うか？

bullet casing, shell casingです。1:18 casings were flying all around us. あたり一面、薬莢だらけだった。

Fort Lauderdale Airport Shootings Leaves At Least 5 Dead

https://www.youtube.com/watch?v=4tV1C2veNBk  1:14 she also found 6 shell casings scattered in front of her home Tuesday morning. 家の前には薬きょう六本が散乱していた。
Shooting leaves Hampton family's car undrivable

練習問題解答
b-0545 spent shell casings
b-0636 a shell casing
b-3288 spent bullet casings