Note she starts out with the Gallant set on 3 round burst, and switches to 5 round burst. The former seems much more effective. Later on she is emptying 4 squeezes of 5 rounds into a single target and it barely goes down. I think the recoil must be enough that on 5 round burst, the last two rounds are not hitting the target. If you plan to double tap each target the way she starts out, that's 9 targets per mag. that's really good. You should never need more than 3 mags total for a mission.
Note the incredible range of the Gallant. She is getting sniper like performance from her weapon. Reason to keep a 4X on it.