History of Full Auto Trigger System

Full Auto Trigger System is a basic weapon trait: holding the trigger fires the weapon at full auto, with a small hidden bump to rate of fire. The Destiny 2 Wiki lists it on Pulse Rifles, Scout Rifles, Grenade Launchers and Shotguns, such as Metronome-52.

It makes sustained damage easier but encourages spray fire, and increases recoil and weakness at range (per the Destiny 2 Wiki).