M810 Helix point defense gun
From Halopedia, the Halo wiki
The AAA Helix Gun was a United Nations Space Command starship-mounted weapon. It was an autocannon found on Human capital ships during the Insurrection and during the Human-Covenant War as late as the Battle of Psi Serpentis in 2543.
Description
The AAA Helix system worked as a point-defense weapon. If provided sufficient range by use of Helix guns that were capable of intercepting incoming missiles and, presumably, boarding and fighter craft. Their description as being "spun up and hot," suggests that they were some kind of gatling gun[1]. They were likely computer or AI-operated, as with virtually all other ship-mounted autocannons.
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