both barrels

Noun

figuratively informal plural plural-only

(informal, figuratively) The maximum damage that a weapon can deliver.

Japanese Meaning

武器が発揮できる最大の破壊力 / 武器が持つ最も強力な攻撃能力

In the final debate she unleashed both barrels on her opponent, and his campaign never recovered.

最終討論で彼女は相手に最大の威力を浴びせ、彼の陣営はその後立ち直れなかった。

Sense（1）

(informal, figuratively) The maximum damage that a weapon can deliver.

to give someone both barrels