From Halopedia, the Halo wiki
Design and development
The Stanchion is equipped with an inertia buffer that helps manage recoil and a bipod that can be folded back and secured on the weapon. The rifle is compatible with an "ATLAS HISHOT PRO-X" smart-link optic.
The weapon has a feed of 7 rounds. These rounds are penetrator darts that are covered in a Sabot, and Storage casing which is "full burn-up".
During the Second Ark Conflict, the M99A2S3 Stanchion was used by Lance Corporal Sparks of Sunray 1-1, and had achieved at least 17 kills with it. Sparks also customized his weapon with tally marks for every kill, a Dazzle camo pattern, and two charms; a Scorpio charm and an ODST Talisman.
List of appearances