Your objective is to score 15 kills using XM1014. As could be expected, XM1014 works best at close range combat, as the shots have extended recoil which is useless at long range combat. The best way to deal with your opponents is hiding behind the corners and taking care of the incoming enemy. The close range will enable you to take care of an opponent with a single blast. Nevertheless, aim for the upper body for maximum effectiveness. Below you can find two advantageous ambush locations.
You can find a set of stairs beyond this corner that end with a narrow passageway along the deck. You can peek from the corner and see if there isn't anyone approaching. If you've noticed any movement, return to your initial position and wait until the enemy comes into view. One close-range shot should be enough to eliminate your target. Moreover, rotating to the left allows you to have eyes on the second corridor that can also be utilized by your opponent.
Climbing the stairs leads you to a low balcony that can also serve as a vantage point. If you've noticed anyone, jump off the balcony and wait behind the corner in order to eliminate him easily.