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Nickdfresh
10-29-2008, 06:11 AM
M4 (5.56mm) Round Has Strong Competitors
October 10, 2008
Tactical Life|by André M. Dall'au

Eugene Stoner and ArmaLite designed and built a lightweight, powerful, small-caliber shoulder weapon after the Army asked for help to develop a 5.56x45mm chambered military rifle in 1957.

The Army, looking ahead to a jungle war in Southeast Asia, picked the lightweight design to equip its new, highly-mobile soldier. But the Army did not fully adopt the specific design requirements that made the original AR-15 operate effectively.

No one recognized that the ball powder substituted by the Pentagon had a greater fouling effect on the AR bolt assembly and chamber area. In addition, troops were not properly trained on how to clean their new rifles. The result was a weapon that was susceptible to jamming in the field, giving the new rifle a bad reputation right off the bat.

The poor initial performance, together with the marginal incapacitating ability of the 5.56 round, led to doubts about the Stoner design that linger today. But the mobile warriors of today are frequently getting in and out of vehicles and need a shorter weapon. The loss of active barrel length in the M4 further cuts the overall effectiveness of particular loads of the 5.56 round that many already considered to be too small and weak.

Recognizing the dilemma, military and civilian manufacturers are developing rounds for the AR platform that could bridge accurate lethality and shorter barrels. Two different approaches are strong contenders: the 6.8 SPC (Special Purpose Cartridge) and the 6.5 Grendel.

Both the 6.8 SPC and 6.5 Grendel have a greater potential for immediate lethality than the 5.56, based on a heavier bullet traveling at a comparable speed. During tests, shots taken at distances ranging from 50 to 75 yards with the 6.5 Grendel at medium-sized wild hogs produced many first-round lethal hits, as well as immediate incapacitation. The bullets did not exit but fragmented during passage through the tissue.

The accuracy of 6.5 Grendel and 6.8 SPC was excellent. The groups for each caliber met or exceeded previously published data. The ability to stay on target during full-auto fire was achievable and far exceeded any similar .308-caliber weapon on hand for controllability. Our overall conclusion is that both the 6.5 Grendel and 6.8 SPC demonstrate superior effectiveness when compared to the 5.56 -- transferring more energy using a larger, purpose-formed bullet.

The 6.8 SPC is a well-engineered combination of velocity, accuracy and reliability for combat engagements up to 500 meters. With a trajectory very similar to the .308 WIN, the 6.8 SPC provides almost 50 percent more downrange, terminal-energy than the 5.56 NATO at 100-200 meters. However, at distances greater than 400 yards, performance of the 6.8 SPC is inferior when put up against the .308 Win or the 6.5 Grendel.

The 6.5 Grendel bullet is designed for energy retention during flight and has about twice the mass of the 5.56 NATO, with ballistics superior to the soviet-era 7.62x39 mm round. It maintains a devastating impact on tissue at longer ranges. The flat-shooting round has demonstrated one minute-of-angle accuracy beyond 600 meters, where the performance of the 6.8 SPC falls off.

Overall, both the 6.5 Grendel and 6.8 SPC offer similar hard-hitting short-and-intermediate range performance with .308 accuracy out to intermediate ranges. The 6.5 Grendel has the edge past 600 meters. Given a choice, I would take the better ballistic bullet of the 6.5 Grendel, which has incapacitating lethality for most tactical situations from CQB to out beyond 600 meters. However, the logistical support for the 6.5 Grendel and 6.8 SPC has been inconsistent. In addition, the demonstrated ability of the 5.56 green-tip to penetrate light armor and steel plate better than the 6.5 Grendel or 6.8 SPC will be of interest to operators who might have to take on technicals when under fire.

Although no single caliber will provide the operator with a solution to every tactical problem, many warriors interviewed would still take the M855 5.56 due to overall satisfactory performance and ammo availability. One of the important aspects of the "is the M4 good enough" argument is to ensure that the "real" trigger-pullers have the loudest voice and overriding opinion about what works in the field.

Panzerknacker
10-29-2008, 06:21 PM
That would interesting to see, but of course something must be done with the huge supply of 5,56mm ammunition still in store, so I dont think we going to see the full adoption of the 6,5 in , let say 10 or 15 years.

tankgeezer
10-29-2008, 07:18 PM
The U.S. usually adopts or leads a motion to adopt a new cartridge if its to be used by the general military services, as Nato has to be considered for the purpose of having common munitions available from any member nation. (thats why they foolishly dropped the 1911-a1 .45 gov't pistol ) For special operations, or situations, they may well adopt a special type of ammo even if it isnt used by other Nato members.

nstoolman1
11-04-2008, 06:14 PM
They can ship all that 5.56 to my house if they want. LOL :)

Clave
11-06-2008, 05:11 PM
I'm still confused as to why they dropped 7.62 - that was proper grown-up ammo... :army:

RifleMan20
11-06-2008, 09:47 PM
When watching a show on the history channel, I saw that the 5.56 did more damage to a human body then a 7.62 round, though confusing I heard the other way around in other stories but their graphic illustration showed that a 5.56 "tumbled" in the body causing more internal damage while the 7.62 practically went straight through.

pdf27
11-07-2008, 01:38 AM
5.56mm doesn't tumble, it breaks into two or three pieces which then go all over the place inside. However, it only does this if it hits a human body at the right angle and with sufficient speed. With short-barreled weapons like the M4 carbine, the bullet will drop below this speed at ranges as short as 50m.

Man of Stoat
11-07-2008, 06:49 AM
For this reason the US Navy special forces units have actually adopted the 77 grain Sierra match king bullet to replace the SS 109. Black Hills ammunition load it for them, and it has significantly increased accuracy and stopping power out of the M4 Carbine. What it lacks over the SS 109 is penetration, e.g. of cover, but the increase in lethality, in their opinion, more than makes up for it.

The match king, by the way, is an open tip match bullet, so constructed as to make the base of the bullet as uniform as possible (not so that it expands -- the game king, on the other hand, is designed to expand). Hence, it was deemed that these bullets do indeed conform to the conventions.

Random trivia: it is the base of the bullet, not the tip of the bullet, that has the biggest effect on accuracy. The tips of the match kings are actually quite raggedy, and people make special tools to remove this. I don't actually know of a single test that anyone has done that has proved that this makes any difference whatsoever!