The Captain's Journal » Paul Harrell: 62 Grain Versus 77 Grain 5.56mm

13 Jun 2021

Paul Harrell: 62 Grain Versus 77 Grain 5.56mm

BY Herschel Smith

3 years, 5 months ago

BLUF: The 77 grain bullets did more damage in the meat targets. But as always, check the ammunition you’re using for zero, accuracy and precision.

Ammunition,AR-15s

Comments

On June 13, 2021 at 9:02 pm, Brad said:

300 ACC solves that problem. Just sayen
On June 14, 2021 at 12:20 am, Georgiaboy61 said:

During the 1993 Battle of the Black Sea, a.k.a. the “Blackhawk Down”incident in Mogadishu, Somalia, elite U.S. Army Rangers, Army Delta Force and Navy SEAL personnel were using 62-grain “green-tip” M855 ammunition in their issue AR-pattern rifles, carbines and SBRs.

Prior to that time, there had been scuttlebutt that the M855/SS109 62-grain round was an inconsistent performer in the field, but in Somalia, those issues came to a head. Our opponents in the battles there, Somali militiamen (nicknamed “Skinnies”) loyal to local warlord Mohamed Farrah Adid – were seen to absorb multiple center-mass hits from M855 and yet remind in the fight.

Since the men reporting these problems weren’t run-of-the-mill line troops, but some of the finest warriors our nation could produce, their complaints were taken seriously and could not brushed-off as a lack of training or something similar.
Throughout the remainder of the decade, studies were commenced to examine the problem.

A number of findings were relevant. First, the .224-caliber projectiles used in the M4/M16 family of weapons are highly-dependent not only upon muzzle velocity to work, but sufficient yaw-induced instability upon encountering a target, to cause tumbling and subsequent fragmentation inside the target. Indeed, this is precisely how Eugene Stoner and his original design team had intended the original 55-grain ammunition for the AR15 to function; its lightweight high-velocity projectile was designed to fragment upon encountering a human target, thereby creating multiple wound channels within the target.

However, with the advent of SS109/M855 62-grain “green-tip,” which had been adopted in 1980 as the new NATO standard cartridge, the design specification called for the new and slightly heavier projectile to be capable of penetrating a standard Warsaw Pact sheet-metal helmet at 500 meters, so the new projectile contained a steel cup or “penetrator” to add mass to the bullet and also enhance its penetrative ability at distance. Not a true armor-piercing round, the new projectile was termed an “enhanced penetrator” round and given a green-tip. Hence, within the FA community, it became known as “green-tip” ammunition.

In order to stabilize the new projectiles found in the SS109/M855 family of cartridges, including 64-grain M856 “orange tip” tracer, it was necessary to adopt barrels with a 1:7 twist rate.

The faster twist rate and enhanced penetration of the M855 round, it was discovered, tended to cause “ice-picking” or so-called “through-and-through” wounds upon certain body types under certain conditions. At close range, high-velocity M855 tended to over-penetrate the slender-framed Somalis rather than fragmenting. If the target was not so wounded in a vital organ or the central nervous system, he could often remain combat-effective and remain in the fight. This is what the Rangers, Delta and the SEALs had seen at Mogadishu.

The small arms establishment within the armed forces therefore sought a solution to these problems in the form of ammunition which would perform better on such missions, and out of the standard M4/M16 family of weapons then predominantly in use. Around the same time, special operations forces within Joint Special Operations Command, or JSOC, began requesting ammunition and weapons which would perform to a higher standard of lethality out of short-barreled weapons and/or suppressed weapons.

Naval Special Warfare Center, Crane, Indiana, and other R&D establishments found some potential solutions.

According to the Hague and Geneva Conventions governing land warfare, to which the U.S. was a signatory, the use of expanding or hollow-point ammunition was/is prohibited in military small arms. Which is to say anti-personnel ammunition expressly designed to mushroom or open, thereby generating a larger wound channel, when compared to standard full-metal jacket or ball ammunition.

Operational experience and terminal ballistic studies had determined that open-tipped match or OTM ammunition, performed exceptionally well according to the parameters being sought by JSOC. Concerns that the ammunition would be ruled illegal under the Hague and Geneva Treaties, however, proved ill-founded, as Judge Advocate General specialists ruled that even though OTM ammunition fragments and produces a wound somewhat similar to genuine HP/expanding ammunition, it was/is legal since it was/is not expressly-designed as such. Open-tipped match is made in such a way that petals of gilding metal are drawn up or closed around the lead core of the bullet, ending in the bullet tip or metplat.

OPM bullets perform extremely well and fragment at a wide range of muzzle velocities, and are not nearly as dependent upon high MV for their terminal effects as traditional bullet designs like M193 and M855. Moreover, these projectiles also work well from short-barreled suppressed weapons of the kind increasingly being seen in the hands of JSOC operators.

Black Hills Ammunition won the contract to supply JSOC with the much-coveted Mk. 262 77-grain OTM round, based off of the 77-grain Sierra Match King BTHP match bullet. Fired from the U.S. Navy Mk. 12 Mod 0/1 special-purpose rifle, the cartridge is lethal out to 700 yards.

Another design which has proven to be quite effective is the 62-grain Mk. 318 Mod 0 SOST (“Special Operations Science and Technology”) barrier-blind round, which is effective at low muzzle velocities out of short-barreled weapons. In brief, the front lead portion of the projectile is designed to fragment and break-up, which enhances performance in soft tissue at low velocity; the latter half of the bullet is bonded solid copper, designed to hold together when encountering hard barriers such as automotive glass and automotive sheet metal.

Mk. 318 Mod 0 is now in use not only by JSOC, but the Marine Corps as well.

Around the same time, there were other developments along the same lines, but using new cartridge designs entirely, such as 300 AAC/Blackout, 6.8 SPC and 6.5 Grendel to name a few – but those are beyond the scope of this article.
On June 14, 2021 at 12:31 am, Georgiaboy61 said:

It also bears mentioning that civilians looking to increase the effectiveness of their personal protection firearms are not limited in their ammunition choices by the Geneva & Hague Conventions, as are uniformed service personnel. Do your due diligence for your local area, vis-a-vis applicable laws, regulations and so forth, but in the vast majority of jurisdictions, expanding/HP ammunition is legal for personal protection and hunting use, in handguns as well as rifles and carbines.

The take-away is that the ammunition you choose should not in any way be an after-thought. Your firearm, whatever it happens to be, exists for the purpose of firing whatever load you choose for the particular purpose in question. So do your homework and choose wisely.
On June 14, 2021 at 8:07 am, Rocketguy said:

This. I always scratch my head at the lethality discussions surrounding mil-spec ammo. Why tie your hands with stuff that’s tied to ancient, misguided rules? I’m a big fan of the Barnes projectiles. No experience with 2-legged critters but they punch above their weight class on medium game so I would expect similar performance in a fight.
On June 14, 2021 at 12:31 pm, NOG said:

Yup. I keep cheap milspec for play/practice and “end of times no re supply coming”. I keep Federal 64gr soft points, Black Hills 68 or 69gr OTM and Black Hills 55 or 60gr soft points for defensive use.
On June 14, 2021 at 2:08 pm, Stuart said:

Nosler 60 gr. Partition bullet in .223 if you are serious with your hunting.
On June 14, 2021 at 4:50 pm, Georgiaboy61 said:

@ Rocketguy

Re: “I always scratch my head at the lethality discussions surrounding mil-spec ammo. Why tie your hands with stuff that’s tied to ancient, misguided rules?”

You aren’t the only one scratching your head. I’ve studied military history for more years than I like to count, and from the start, I have never understood the convoluted logic which says that HP/expanding small-arms ammo is inhumane for the purposes of warfare, but that there’s nothing wrong with using Claymore mines or napalm for those same purposes.

The closest I can get to some sort of answer is that Europeans of that time – the mid-late 1800s – still adhered to some of the old notions about personal honor and the settlement of disputes on the battlefield or via force of arms. They were attempting to impose rules upon something which is inherently chaotic and ipso facto outside the norms of civilized conduct. General William T. Sherman was right: “War is cruelty. There is no use trying to reform it. The crueler it is, the sooner it will be over.”

Oh, and you are right: Barnes rocks… they make great products.
On June 14, 2021 at 7:14 pm, Rocketguy said:

@GB – I sort of understand the whole Geneva Convention thing. Mainly, I was questioning civilians limiting themselves to rounds that conform. I give the MK262 and similar rounds a pass because they’re more about accuracy…but if I ever find myself dipping into the 193 and 855 stash for a fight, I’ve already done a helll of a lot of shooting.
On June 15, 2021 at 12:24 am, Silence DoGood said:

There’s not a single damn word about bullets in the Geneva Conventions.
On June 15, 2021 at 1:41 am, Georgiaboy61 said:

@ Silence DoGood

Re: “There’s not a single damn word about bullets in the Geneva Conventions.”

OK, what about the Hague Conventions? Mil.gov follows the proscription (prohibition) of said types of bullets, and has since forever, so it had to come from somewhere. Any JAG officers or lawyers in the house?
On June 16, 2021 at 10:58 pm, The Wretched Dog said:

Hague convention. See:

https://avalon.law.yale.edu/19th_century/dec99-03.asp
“The Contracting Parties agree to abstain from the use of bullets which expand or flatten easily in the human body, such as bullets with a hard envelope which does not entirely cover the core, or is pierced with incisions.”

and

https://www.icrc.org/en/doc/assets/files/other/irrc_849_coupland_et_loye.pdf
On June 17, 2021 at 6:45 pm, Fred said:

It’s VERY important to note that an international convention agreed upon by the the Senate can NOT modify the constitution.

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This article is filed under the category(s) Ammunition,AR-15s and was published June 13th, 2021 by Herschel Smith.

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