This is my Rifle, This is my Gun Achievement in Halo: The Master Chief Collection

When this mission begins, you will have the Assault Rifle and Magnum automatically equipped by default. This achievement requires you to carry at least one of these weapons to the end of the mission, without ever dropping it for a replacement. Take note that if you run out of ammo, you’ll have to make due with a secondary weapon.

Overall, it’s highly recommended on working towards this achievement on the Heroic difficulty while keeping the Magnum throughout the course of this mission. It’s an extremely effective weapon in picking off Crawlers and Watchers from afar and even pulling off quick headshots on Knights if they are weak. You can ditch the Assault Rifle at any time for something a little more accurate; this includes Forerunner weaponry such as the Light Rifle or Scattershot.

If for whatever reason you accidently drop the weapon of choice for this achievement, you can always revert your save to the last checkpoint. Once the mission’s final cutscene has concluded, this achievement will unlock.