The MA3 Assault rifle was the predecessor of the MA5B Assault rifle used by the UNSC Marine Corps. These weapons were obsolete when the MA5B was produced, due to the MA5B being capable of being stripped down or reconfigured in different ways for various missions. The MA5B becomes an MA2B Assault Rifle when its excess components are removed.
As of 2552, the MA3 Assault rifle was in the black market. They were notably used by the Eridanus Rebels for the security forces of Eridanus secundus. When John-117 returned to the base, the rebel guards were using MA3s, which replaced the HMG-38 Rifle model that they were previously using.