The above photo was found with this caption:

National Liberation Front irregulars (Viet Cong, or VC) training with a variety of rifles in a likely staged photo, reportedly taken in the Southeast Region, March 1967 (note that M14). Unknown photo provenance. Access to North Vietnamese documents and scholarship subsequent to the war has blurred the distinction between the two organizations, as most VC were, in fact, NVA. Though particularly true after the Tet Offensive, the blurring was already underway in 1966.

The M14E2 came out of the US Army Infantry board's dissatisfaction with the M14 with a bipod's performance as an automatic rifle by early 1962, and by that time the M15 had been canceled.

The board had a prototype made by modifying a standard M14, which came to be known as the USIAB rifle. The handgrip, stock, and sling were redesigned. The stock was meant to provide in-line recoil. A muzzle device to stabilize the rifle in full automatic fire was fitted.

After all the changes had been finalized, the new design was fielded as the M14E2, and the designation for adoption was changed to M14A1 in 1966.