M53 non-lethal round
From Halopedia, the Halo wiki
M53 non-lethal rounds are human non-lethal ammunition used for incapacitating targets.
On Sedran Colonel Randall Aiken's orders, the Sedran Colonial Guard-Office of Naval Intelligence unit planned to use them on Arris Le and Haisal Wari during the Mission to Alpha Shard but the smugglers ran before the team could shoot.
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