M6A magnum
From Halopedia, the Halo wiki
The M6A Handgun[1] is a United Nations Space Command firearm.
It is a variant of Misriah Armory's M6 Series of sidearms, and is noted for its comfortability. However, it sees only widespread distribution in civilian security forces such as police, not mainstream UNSC military units.
The M6A Handgun is believed to fire 12.7mm x 40 projectile ammunition, possibly semi-armor piercing (SAP). But the M6A might actually fire a smaller round because they are more comfortable to shoot.
It has also been around for 140 years before 2552, meaning it was made in 2412.
