This article is an excerpt from the Gun Digest Book of Classic Combat Rifles.
After the AR15 — now, the M16 rifle — went into circulation, more was learned about how to improve the rifle. The rifling twist was changed from 1:14 inches to 1:12 inches. The Army wanted a manual bolt closure device added so, if the bolt failed to lock, it could be manually closed — and the forward assist assembly was born. The firing pin was lightened to prevent slam-fires (caused by the inertia of the firing pin when the bolt closed on a round). The buffer was changed from the original hollow version to one with weights in it to prevent the bolt from bouncing back when it slammed into the barrel extension.
On November 4, 1963, Colt was awarded a contract worth $13.5 million dollars for the procurement of 104,000 rifles … the legendary “One Time Buy.” Of those rifles, 19,000 were M16s for the Air Force and 85,000 were the XM16E1 (with the bolt closure device/forward assist assembly) for the Army and Marines. The XM16E1 was adopted as the M16A1 rifle. Steps were taken to procure ammunition.
Procurement of the ammunition is one of the main factors in the rifle’s performance early in the Vietnam War. The initial ammunition used by DOD was made to Armalite/Colt specifications that called for IMR 4475 propellant.
The weapon’s reputation for durability and reliability was based on this ammo/extruded propellant combination. However, the military wanted to standardize propellants and the propellant used in the established 7.62×51mm NATO cartridge was Ball powder manufactured by Olin Corporation. So, when ammunition was ordered, Olin’s Ball powder was used for the new 5.56×45mm M193 Ball cartridge. Both powders created the desired 50,750 psi.
Ball (spherical) powder reaches its peak pressure significantly faster than extruded IMR powder. Ball powder generates larger amounts of carbon residue that clogs the gas tube and barrel port, causing the firearm to malfunction. The most serious malfunctions, during the early use of Ball powder, involved extraction problems and a significant increase in the cyclic rate of fire. Despite having this information, the Department Of Defense still approved use of Ball powder.
Gene Stoner was approached by Frank Vee of the OSD Comptrollers office after the package was approved and asked what he (Gene Stoner) thought of the use of Ball powder. Stoner asked, “Why are you asking me now?” Vee said, “I would have felt better if you would have approved the package.” Stoner replied, “Well, now we both don’t feel so good.”
The “one-time buy” was now a thing of the past. The original $13.5 million contract turned into a $17,994,694.23 contract. There were an additional 33,500 rifles that went to the Air Force, 240 to the Navy and 82 to the Coast Guard. Over $517,000 worth of spare parts was ordered.
The first field performance reports, from the 5th Special Forces in Vietnam, were excellent. The rifle had been well received and was very popular, although instruction manuals were in “short supply.” During the investigation by the Ichord Subcommittee of the M16 Rifle Program, Honorable Richard Ichord said — regarding the rifle’s reputation with the North Vietnamese Army and Vietcong — “I understand that they refer to this rifle as ‘black rifle,’…I have heard their motto is ‘Beware of the units with the black rifles’… they have been possessed with deadly fear.”