Cold War Guns: The XM16E1 Rifle

There is some debate regarding the official beginning of the Cold War between the west and NATO and the Soviet Union and the Warsaw Pact countries. Some have said that the Truman Doctrine of 1947 discouraging Soviet expansion was the start. Others state that it was not until the Warsaw Pact Agreement of 1955. Others state that the Tri-Continental Conference held in Havana, Cuba in 1966 pushed the Cold War to “heat up”. 

Regardless of who is right, the Cold War was essentially a series of proxy wars between the United States and NATO and the USSR and its Warsaw Pact allies from the end of WWII until the fall of the Berlin Wall in November of 1989 which signaled the collapse of the Soviet Union. Speaking of which, the construction of the Berlin Wall in 1961 was also viewed as a major provocation by the USSR during the Cold War. 

Some of the major proxy wars fought during the Cold War were the Korean War (Korean conflict), the Vietnam War (Vietnam police action), the Rhodesian Bush War, the Angolan Civil War, the Afghan-Soviet War, and the Nicaraguan revolution. 

Keep in mind, the United States Congress hasn’t signed a formal declaration of war since June 4, 1942 when it declared war against Romania, Bulgaria, and Hungary. All other “wars” since that time have been “use of force” authorizations. Don’t believe me? Look it up.

As the Cold War was a significant era for the United States and the rest of world and the weapons developed and used during that era have some unique history and stories, my illustrious editor has given me the green light to do a series of articles featuring Cold War era guns. 

AR-15 Becomes the XM16E1

Everyone reading this should know that the Armalite Rifle Model 15 was developed by Eugene Stoner and his team as a 5.56x45mm NATO alternative to his original AR-10 in 7.62x51mm NATO. Back in 1959, Armalite sold the manufacturing rights for the AR-15 to Colt’s Manufacturing and that company began developing a 5.56mm NATO replacement for the M14. 

As you may know, before the US Army, the primary procurement arm for the US Department of Defense, commits to full adoption of any firearm, it’s standard practice to first field “XM” versions in the field to wring out any shortcomings and make improvements. The military designation of “X” or “XM” simply means experimental or experimental model. 

Before the US Army fully adopted the M16A1 rifle, they first sent the XM16E1 (in the military the “E” is pronounced “Echo” when describing the item) to the jungles of Vietnam. 

The XM16E1 was a serious departure from the guns of WWII that were constructed primarily of steel and hardwood. Gene Stoner had worked in the aircraft industry and brought his knowledge of high strength, lightweight materials to Armalite. While steel was used for important parts, such as the barrel and bolt carrier group, other parts were made of non-corrosive and lighter aircraft grade aluminum. High strength polymer, that didn’t swell in heat and humidity and was a fraction of the weight of hardwood, was used for the grip, stock, and forearm.

In today’s world that seems obvious, but in 1959 such a thing was truly out-of-the-box thinking. Also, the Army had been essentially married to the “Garand action” since WWII and Stoner’s “direct gas impingement” was both new and suspect to the old WWII veterans.

Keep in mind that Secretary of Defense Robert McNamara and the “Whiz Kids”, his personal think tank group, were looking for “new and modern” for the DOD. Despite the misgivings of WWII era generals, McNamara liked the AR-15 and pushed the project forward. 

In 1961, Secretary McNamara authorized the purchase of 1000 AR-15 rifles. The first of these rifles to ship to Vietnam still had “Colt AR-15” inscribed on the lower receivers along with “U.S. Govt M16E1.” As a side note, while training troops for combat deployment during GWoT, I came across a student with an “M16E1” lower receiver onto which an M16A2 upper had been installed. 

XM16E1 Specifics

The XM16E1 had the unique carrying handle upper receiver that had a rear peep sight that was adjustable for windage using a “drum” on the right side. As was Stoner’s desire, the windage drum was adjusted using the tip of a 5.56mm FMJ cartridge. Elevation was adjusted by a five-position round front sight post, again using a cartridge tip. The square front sight post with four-position adjustment came with the M16A2. 

The aluminum lower receiver didn’t have the “fence” around the magazine release button and the forward assist was a paddle shape, rather than the button most modern shooters are familiar with today. 

At the business end of the barrel was a three-prong “split brake” that acted as a very effective flash hider/compensator. The birdcage muzzle device of the M16A1 came later and the split brake is one of the easiest ways to identify the XM rifle from the M16 in old black and white photos from that era. Also, the original bolt carrier groups were chrome finished, not parkerized as they would be later. 

The triangular forend pieces were left and right with aluminum heat shields and that stock was solid, without a cleaning kit storage compartment. By the time of the Vietnam War, the US Army had begun to use ammunition with non-corrosive primers versus the corrosive ones used in WWII and Korea.

The non-corrosive ammunition and the use of aluminum and polymer were likely two of the reasons the DoD neglected to issue cleaning kits to the troops or teach them detailed maintenance and cleaning. That error proved to be a disaster for the men in the field. 

STANAG and 20-Round Mags

One of the major advancements of the NATO alliance was the Standardization Agreement (STANAG). NATO countries agreed to all use the same field gear, training, communications equipment and small arms ammunition. The first NATO STANAG rifle round was the 7.62x51mm. However, the Soviets were fielding their troops with the smaller 7.62x39mm round and the standard loadout for Soviets, and subsequently the North Vietnamese Army, was higher than US troops with M14s and 7.62 ammo.

The decision was made that US troops needed to be able to carry more ammunition for the same amount of weight. While many European NATO countries clung to the 7.62 round, the DoD wanted a new rifle round…hence 5.56x45mm NATO was rushed into action.

Keep in mind that all the NATO battle rifles at the time — the M14, FN FAL, and G3 — had standard magazines that held 20 rounds. Twenty rounds seemed to be the accepted standard at the time, thus the first aluminum magazines for the AR-15/M16E1 were 20-round versions. The 30-round M16 magazines were shipped to Vietnam during the closing years of the war, but all the major battles from 1965 to 1969 were fought by US troops using 20-rounders. Consider the Battle of the Ia Drang Valley and the Tet Offensive.

Interestingly, the M16E1 was issued so fast that dedicated 20-round magazine pouches hadn’t been developed. Instead, the troops in the field used the existing 20-round M14 pouches. The M14 pouches were deeper than they needed to be for the AR mags and troops learned to shove rags or field bandages in the bottom of the pouches in order to keep the magazines high enough to be rapidly grabbed during the heat of battle. Also, the OD green cloth bandoliers that the 5.56mm ammo came in could be used to carry spare 20-round magazines. 

A Storied History

Despite the consternation of the WWII old guard about fielding a “plastic toy” or a “Mattel Death Trap,” the AR-15/M16 rifle ultimately proved to be a reliable and deadly tool for the US military for better than sixty years. Additionally, the direct gas impingement action, while hated and decried by many old school veterans, didn’t fall by the wayside. 

Also, let’s not forget that the 5.56mm round, denigrated as a “gopher round” by those old timers, has proven to be very effective. This was particularly true when Black Hills Ammunition developed the Mk262 MOD 1-C with its 77 grain OTM (open-tipped match) projectile. Special operations forces stacked bodies in Iraq and Afghanistan with that cartridge and it’s still the go-to round today. The Marine Corps’ Mk 318 MOD O round has a similarly lethal track record. 

The M16E1 wasn’t perfect, but the lessons we learned from using that rifle in genuine combat have led us to where we are today, making it an extremely important Cold War Era gun. 

Specifications: XM16E1 Rifle

Caliber: 5.56x45mm NATO
Action: Select Fire
Capacity: 20 rounds (and 30 and others)
Barrel Length: 20 inches
Overall Length: 38.8 inches
Weight (empty): 6.37 pounds
Furniture: High Strength, Black Polymer

 

Paul G. Markel is a combat decorated United States Marine veteran. He is also the founder of Student the Gun University and has been teaching Small Arms & Tactics to military personnel, police officers, and citizens for over three decades.