Halo Alpha
Halo Alpha

Just relaxing up here with my new best friend, Gunny. Nothing like an M99.

The M99 Special Application Scoped Rifle, also referred to as the M99 Stanchion Gauss Rifle or simply the Stanchion, was a United Nations Space Command anti-matériel rifle.[2][4]


The technology used in the M99 is practically the same concept used on the larger Mass Drivers and MAC, but on a greatly reduced scale. This system works through using a series of electromagnetic coils (an Asynch Linear-Induction Motor) rather than chemical propellants as a source of kinetic energy, and is very similar to the M68 Gauss Cannon. A weapon which utilizes this technology is, needless to say, very powerful.

The M99 is also used with a portable computer to provide the ballistic calculations necessary to engage long range targets. The rifle can also be integrated with other systems, such as ARGUS Drones for trajectory and ballistic data. The M99 also uses the ATLAS+ system developed by Ohana.[2]


The 5.4mm/.21 caliber round is very small in comparison to most standard firearms of the era, but using the Gauss technology, the small rounds have the ability to rip targets apart, even through office buildings.[5] This is due to the high force imparted on the round. The round creates shockwaves as it passes through the target. In the case of material targets, this is a minor explosion. In the case of personnel, it simultaneously rips apart and pulverizes the body around the impact area. Even hits on the extremities can be deadly.

The rounds have been known to have the ability to travel great distances without affecting the trajectory, delivering enough force to punch through instacrete pylons, blow a human apart, and continue on course through an abandoned parking lot.

Operational History

The Model 99 Special Application Scoped Rifle first entered production in 2491,[2] and its production was ceased in 2521.[2] It appears to have been a popular rifle, as per its production length, and it was used mainly for anti-materiel operations. However, the .21 caliber round shot at a velocity of 15,000 meters per second was very effective against "soft" targets.[5]

The M99 Stanchion was used by then-Corporal Avery J. Johnson during Operation: KALEIDOSCOPE, who used the weapon to assassinate Jerald Mulkey Ander, a member of the Secessionist Union from a significant distance. He used another M99 Stanchion during Operation: TREBUCHET on Tribute to kill an Insurrectionist terrorist driving a truck rigged as an explosive, and attempted to use it to neutralize a second terrorist inside a nearby restaurant, the Jim Dandy. His first target was successfully killed and torn apart by the force. The second target, who was holding a boy as hostage, killed herself with a bomb she had hidden in the restaurant, along with three special warfare Marines and thirty-eight civilians.[4]

At some point, the UNSC Spirit of Fire would acquire several Stanchions and supply them to their sniper forces.[6]

In 2558, while helping defend Cassidy III from a Guardian, Spartan Romeo would ask the Front troops he was assisting for any snipers they had available. They would give him an out of production M99 Stanchion.[7]