Direct proof of use
Conflict Armament Research documented a Bushmaster XM15-E2S rifle in its August 2014 field investigation of weapons captured from Islamic State forces in Iraq and Syria. In Case 3 of the dispatch, CAR reported that Kurdish YPG forces captured several small arms from Islamic State forces north of Bara in the Sinjar Mountains, Iraq, on 4 August 2014 and that CAR documented the materiel on 11 August 2014.
The listed materiel included one U.S. XM15-E2S 5.56 x 45 mm semi-automatic rifle manufactured by Bushmaster Firearms International. The record therefore supports an Islamic State conflict-use entry as captured or recovered materiel; it does not identify a specific firing incident involving that individual rifle.
Sources: CAR 2014 Islamic State Weapons Dispatch, CAR 2014 Islamic State Weapons PDF
Timeline
CAR described the dispatch as a preliminary examination of weapons and ammunition captured from Islamic State forces between mid-June and early August 2014, during Islamic State operations in northern Syria and offensives around Mosul and Sinjar in Iraq.
The Bushmaster rifle appears in the north-western Iraq case. The YPG capture date given for that case is 4 August 2014, and CAR's field team documented the captured small arms one week later, on 11 August 2014.
Sources: CAR 2014 Islamic State Weapons Dispatch, CAR 2014 Islamic State Weapons PDF
Narrative
The XM15-E2S was a comparatively uncommon item in the Islamic State small-arms sample. CAR's later three-year report found that most recovered Islamic State weapons in Iraq and Syria were Warsaw Pact-calibre arms, while 5.56 x 45 mm rifles and carbines formed only a small fraction of the weapons documented.
CAR also noted that recovered U.S.-manufactured weapons accounted for only a small proportion of Islamic State holdings in Iraq and Syria, despite the visibility of U.S.-made rifles in Islamic State propaganda and reporting on weapons captured from Iraqi military units. For the XM15-E2S, the directly supported battlefield record is the August 2014 recovery north of Bara rather than a complete chain of custody or inventory count.
Sources: CAR 2014 Islamic State Weapons PDF, CAR 2017 Weapons of the Islamic State
