AR-15/M16: The Rifle That Was Never Supposed to Be

The CAR15 (Colt Automatic Rifle 15) gained major popularity with the development of the new M4 and M4A1 carbine. Note the telescoping stock and the shorter barrel. Most CAR15 rifles were issued with a 14.5-inch barrel.

The CAR15 (Colt Automatic Rifle 15) gained major popularity with the development of the new M4 and M4A1 carbine. Note the telescoping stock and the shorter barrel. Most CAR15 rifles were issued with a 14.5-inch barrel.

This article is an excerpt from the Gun Digest Book of Classic Combat Rifles.

Chrome-lining the barrels gave three major improvements to the standard barrel. First, the chrome-lined barrel was corrosion resistant. Second, chrome is slippery in nature and assists in extraction and ejection. When chromed, the walls of the chamber are harder; sand and mud don’t “iron” into them. Thirdly, chrome is 2 to 3 times harder than standard barrel steel so the barrel lasts significantly longer.

The new, improved M16/M16A1 barrel assemblies would have stamped on the barrel, in front of the front sight assembly: “C” (Chrome Chamber Only), “C MP B” (Chrome Chamber, Barrel & Magnetic Resonance Tested) or “C MP Chrome Bore”(Chrome Chamber, Barrel & Magnetic Resonance Tested). Many experts, including Bill Davis, felt the failure to chrome the chamber was responsible for many of the early malfunctions in Vietnam.

The flash hider was changed from the early three-prong to the new “bird cage” style. The three-prong suppressor was superior to the new design, but was snagprone in the field. With these modifications in place, the M16/M16A1 rifle was “perfected” and performing to the Department of Defense acceptance standards.

The AR15/M16 Carbines

Soon there was a demand for a smaller, more compact, version of the rifle. Early in 1966, the Army expressed interest for a carbine for its special operation units, placing an order totaling some 2,050 carbines. Lieutenant Col. Yout later ordered an additional 765 Colt “Commandos” — and a new name was coined for the carbine project. The first carbines were known as CAR15 (Colt Automatic Rifle). These first designs incorporated a 10-inch barrel and a sliding butt stock. Later the barrel was changed to 11.4 inches to permit the weapon to launch grenades. The Army signed a contract for 2,815 “Commando model” submachine guns on June 28, 1966.

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This article is an excerpt from the Gun Digest Book of Classic Combat Rifles. Click the cover to order this book and read more gun histories.

As expected, the CAR15 — now the XM177E2 — successfully passed all testing phases at Aberdeen Proving Ground. However, a new problem appeared: the deafening noise and large fireball from the muzzle, thanks to the CAR15’s higher cyclic rate of 700 to 1,000 rounds per minute. As a remedy, many of these rifles were equipped with 14.5-inch barrels, a practice that carried over to the M4 project of the early 1980s.
Product Improvement (PIP)

On October 28, 1980, there was a new 5.56×45mm cartridge on the block. NATO (Northern Atlantic Treaty Organization) had adopted the Belgian-made SS109. This new bullet had two major differences from the GI 5.56×45mm M193 Ball cartridge. First, the bullet weighed 62 grains instead of 55 grains. Second, this new bullet had a hardened steel penetrator core, giving this new 5.56×45mm round better penetration at all distances than the 7.62×51mm NATO (M80 Ball) round.This new SS109 round penetrated three 3.5mm mild steel plates at 640 meters and a U.S. issue helmet at 1,300 meters.

The new 5.56×45mmNATO round revolutionized military small arms ammunition all over the world. In 1974, the Soviet Union switched from the 7.62×39mm (AK47/AKM) to the 5.45×39mm Soviet round of the new AK74 rifle. This new round was a .221-inch diameter 52-grain full metal jacket boat-tail armor-piercing bullet with a velocity of 3000fps.

The new SS109 round was more lethal than the original M193 Ball round due to the faster “spin” and fragmentation upon impact with soft tissue.

4 thoughts on “AR-15/M16: The Rifle That Was Never Supposed to Be

  1. master gunny

    As the armorer for the 6th Engineer Bn I one had to use a hammer and screwdriver to force the bolt into full battery (with a round in the chamber!) in order to clear a malfunction. I was shocked because the weapons was not anywhere dirty enough to explain the severe malfunction. That same day I have another stoppage, same problem, but again the fowling was not that severe. I could go on and on with why I feel the weapon is a poor choice for an infantrymen but suffice to say that I will stick with my M1A and HK-91.

  2. master gunny

    With respects it’s obvious to me that you guys are too young to remember the controversy surrounding the introduction of the M-16. Not mentioned in yourt article were the constant complaints about the weapons, their unreliability, the congressional hearings on the malfunctions that that were literally getting our tropps killed in Vietnam. Numerous accounts of troops found dead in their fighting holes with their weapons diassembled were presented as evidence that the weapon was despised by the troops. Mothers would get urgent letters from their sons asking for cleaning gear and solvents because the weapons fouled so easily and severely. The forward assist, and chrome chamber were just a couple of the modifications necessary to solve some of the problems.

    More offensive to me was the remark that the M14 was prone to jams and problems and speaking from experience I can tell you that is exactly the opposite of the truth. The M14 was rock solid reliable, accurate, and robust. The M1-16 fragile, unreliable, ualofre

  3. tinock28

    I liked the article on the AR-15/M16 rifle very much, I remember an article back in 1956-57 in one of Gun Mag’s about the AR-10, I thougt at the time it was a good rifle.

    1. master gunny

      Read Colonel Moore’s book, “We were soldiers one and Young” to get a better understanding of how critical reliability is to a grunt. One passage, regarding Lt. Herricks surounded platoon, say it all. Troops fighting for their lives against overwhelming odds were forced to discard their weapons and pick up those of their wounded comrades in order to stay in the fight. Many times those weapons were also not functioning and so the troops had to rummage through the perimeter to find a working weapon. Trust me, that sucks