Author Topic: Army vs. Marines: Which Service Had the Better Bullet?  (Read 346 times)

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Army vs. Marines: Which Service Had the Better Bullet?
« on: February 26, 2019, 10:37:25 pm »
National Interest by Charlie Gao 1/27/2019

We take a look.

In Mark Bowden’s book, Black Hawk Down, he describes an incident where a soldier’s CAR-15 5.56mm carbine failed to put down an enemy combatant despite multiple hits to center mass. The ammunition used by the soldier was the M855 “green-tip” projectile, adopted by the U.S. Army and Marines in the 1980s.

Further reports of M855 underperforming lead the U.S. military on a hunt for a new cartridge that would be more effective. Surprisingly, the Army and Marines diverged in their approach, and for nearly half a decade both services fielded different cartridges as standard issue to their troops until Congress forced the Marines to use the Army round.

But which round is better? Have other NATO countries kept up with these innovations and developed “third-generation” 5.56 rounds of their own? Why did the Marines resist the change for so long?

To understand the problems with the M855, it’s worth looking at the round it replaced, the M193. The M193 was the cartridge the original M16 was designed for. It uses a fifty-five grain lead projectile with a copper jacket. It is designed to be stabilized by the 1:12 twist and twenty inches of the M16’s original barrel. The primary wounding mechanism of this projectile is yawing and fragmenting upon impact with flesh, both of which create a larger wound cavity than simply passing through.

The M193 was also adopted by a variety of other nations. Almost every nation that used the original M16 or M16A1, from the Republic of Korea to the United Kingdom utilized M193. France also adopted a 5.56mm round similar to the M193 in 1979, which also used a fifty-five grain projectile in a 1:12 twist barrel. However, due to the violent nature of the French rifles’ actions, the French cartridge utilized a steel case instead of brass.

But the M193 was not a NATO standard. In 1970, noting that the United States had diverged from the earlier 7.62x51mm standard cartridge, NATO wanted to re-standardize a single type of small arms ammunition and conducted their own series of tests from 1973 to 1979 with a variety of smaller “intermediate” cartridges in the same power range as the M193.

The trials involved firing at steel helmets at extended range, which caused rounds to be optimized for long-range ballistics and penetration on steel rather than terminal ballistics on soft targets.

The competitors were a British 4.85mm round, a German 4.7mm caseless round, and two variants of 5.56, one from America and one from Belgium. The Belgian round, the SS109, won the trials and was designated as the standard NATO infantry rifle cartridge under NATO Standardization Agreement (STANAG) 4172 in 1980. Most NATO nations adopted the SS109 as their first 5.56 round. The United States adopted it as the M855, painting the tip green to allow soldiers to easily differentiate it from older M193 ammunition.

The M855 uses a sixty-two grain projectile stabilized by a 1:7 twist barrel. The slower twist rate is required to stabilize the heavier projectile. The projectile has an enclosed steel penetrator that gives it superior penetration against steel. The round fragments upon hitting a soft target, but it requires a significant amount of velocity to do so.

The round was paired with the new M16A2 rifle, which combined a barrel that used the new twist rate with various other changes. The old M193 ammo was not backwards compatible with the M16A2, as the lighter ammo would not be stabilized and would yaw significantly in flight leading to poor accuracy.       

The M16A2 and M855 combination was used by the U.S. Army and the U.S. Marines through the 1980s and into the 1990s. But during the 1990s the U.S. military began purchasing short barrel 5.56 carbines again, following poor experiences by special operations forces trying to use 9mm submachine guns in conventional direct action raids.

These carbines had shorter barrels, usually around 14.5 or sixteen inches, which gave them lower muzzle velocity compared to the full twenty-inch barrel of the M16. The lower velocity of these carbines led to incidents such as those in Mogadishu where the M855 fired out of a CAR-15 failed to fragment and put targets down reliably.

The issue of M855 lethality continued to plague the military in the post-9/11 era. As the wars in Iraq and Afghanistan dragged on, the U.S. Army and Marines began to issue out M4 Carbines, which use a 14.5-inch barrel, in larger numbers. This only exacerbated the problem with M855.

More: https://nationalinterest.org/blog/buzz/army-vs-marines-which-service-had-better-bullet-42492