The United States Marine Corps has finally officially announced its adoption of the 5.56mm M855A1 EPR round, developed in the late 2000s by the US Army, marking an important step towards ammunition commonality between the two services. Until now, the USMC has officially only used the legacy M855 round, and to a more limited extent the SOCOM-developed Mk. 318 SOST round, refusing to adopt the US Army’s new M855A1. The Marine Corps Times reports that the Corps’ Combat Development Command has begun procuring the round for stockpiles, with its official adoption coming in 2018:

The Marine Corps will begin ­procuring the enhanced round for its combat stockpiles this fiscal year, said ­Woodburn. ­Deployed Marines who are ­issued M855A1 rounds can use them now.

The M855A1 round, which offers greatly enhanced barrier penetration and more consistent lethality than legacy M855 ammunition, generated controversy when early versions caused significant issues in the USMC’s then-new M27 Infantry Automatic Rifles. Specifically, when combined with legacy USGI magazines, the exposed hardened penetrators of the M855A1 round would prematurely erode the M27’s tighter forcing cone. An anonymous source told TFB that the USMC’s adoption of the Magpul PMag, which virtually eliminates the erosion issue, was a major step towards the adoption of the M855A1 itself. Further, for logistical reasons, the source said that the USMC has been quietly using M855A1 in theater for months already, with good success. Lt. Col. (ret.) Chris Woodburn spoke highly of the M855A1’s lethality: