Shāng le yāo zhīhòu, tā zìcháo chéng le ge xiāhuǒbīng.
After injuring his back, he joked about having become a spent-shell soldier.
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memory
瞎火 is a dud shell - one that won't fire. A 瞎火兵 is a soldier no longer fit to shoot back. Pointed military image, now used more broadly for someone who's lost their edge.