Essentially a heavily modified M16 rifle, it is intended to provide SEAL snipers and designated marksmen with a versatile, accurate, lightweight, and relatively compact weapon chambered in 5.56×45mm NATO.

[6] Developed in-house by SEAL team armorers,[7] the rifle was centered less around a rigid specification and more around the concept of an accurized rifle that could share the duties and ammunition of fielded M4 carbines, whilst also being able to engage targets beyond the carbines' range.

[8] When further development was handed over to Naval Surface Warfare Center Crane Division,[2][9] the United States Army incorporated their own concepts and funding into the joint program, resulting in the Mk 12 Special Purpose Rifle which many SEALs were disappointed with.

[13] These barrels were mated to flat-top upper receivers featuring an M1913 rail, to which optics and back-up iron sights could be attached.

Operators commonly chose to install back-up iron sights manufactured by Knight's Armament Company, ARMS Inc, and Troy Industries with the rifles.