Is the 5.56 history? Will the 6.8 Rem replace it?


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Hokkmike
March 8, 2006, 10:09 AM
(By Chuck Hawks)

The inadequacies of the 5.56mm NATO as a service rifle cartridge are well documented and have inspired many suggestions regarding possible replacements (some on this web site). Apparently someone in the U.S. Special Operations Command also realized the need for a more potent round and initiated work on a new cartridge designed to work in the M16 action.

The new .270 caliber (6.8mm) cartridge is the result of at least a two year cooperative effort between Special Operations, the Army Marksmanship Unit, and Remington. Various calibers from .22 to .30 were tested before settling on a standard .277" diameter bullet, the same bullet diameter made famous in the .270 Winchester.

Remington is offering four 6.8mm SPC factory loads, all with 115 grain bullets. These include two target loads, a Core-Lokt Ultra hunting load, and a Metal Case military-type load. No varmint load is included. The four factory loads all have a muzzle velocity (MV) of 2800 fps and a muzzle energy (ME) of 2002 ft. lbs. from a 24" test barrel. At 100 yards the metal case bullet (BC .325) has a remaining velocity of 2523 fps and energy of 1625 ft. lbs. At 200 yards the velocity is 2262 fps and the energy 1307 ft. lbs. And at 300 yards the velocity is 2017 fps and the remaining energy 1039 ft. lbs. These figures are taken from Remington's 2004 catalog.

The trajectory of the metal case bullet looks like this: +1.2" at 50 yards, +2.7" at 100 yards, + 2.8" at 150 yards, +1.4" at 200 yards, -3" at 267 yards, and -6.6" at 300 yards. The maximum point blank range (+/- 3") is thus 267 yards. These figures are computed for a rifle with a telescopic sight mounted 1.5" over the bore. This, just like the Army claimed, is similar to the trajectory of the .308 with a 150 grain bullet.

The lighter weight .277" varmint and hunting bullets will presumably be the most popular choices in the 6.8mm SPC, and the latter are not thick on the ground. Suggested examples include the 90 grain Speer HP varmint bullet, 100 grain Barnes X-Bullet, 115 grain Sierra HPBT, 115 grain Remington Core-Lokt Ultra, and 120 grain Barnes X-Bullet.

(from another source)

It would appear that military operators would have good reason to have confidence in the 6.8x43mm SPC. According to noted gunwriter Gary Paul Johnston, "For military purposes, the 6.8mm SPC outshoots anything in its class--including the 5.45x39mm, 5.8x43mm [Chinese Army's standard infantry rifle cartridge], 7.62x39mm, and even the 6.5mm Grendel. Producing increased incapacitation at all ranges out to 600+ yards, the 6.8mm round fires a 115-grain Hornady Match or Sierra Match .270 caliber bullet at over 2600 fps (feet per second) from a 16-inch barrel M16 type rifle called the Mk-12 Variant "Recce", and has essentially the same trjectory as the M118 7.62mm NATO Match cartridge. A conceptual 6.8mm SPC version of the Special Purpose Rifle (SPR) also exists. The 6.8mm SPC is at least as accurate as the 5.56mm NATO and 7.62mm NATO rounds now used by U.S. Military Forces." (November 2004 Issue of "Guns & Weapons for Law Enforcement" Magazine, p.62).

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pauli
March 8, 2006, 10:19 AM
/me makes popcorn

High Planes Drifter
March 8, 2006, 10:19 AM
I scincerely doubt it; at least anytime in the foreseable future.

jd25q
March 8, 2006, 10:53 AM
The problem with the 6.8mm is the bullets have low sectional densities and low ballistics coefficients. They are very light in the .270 line. Both of these qualities hurt long range performance.

cgv69
March 8, 2006, 11:04 AM
At this point, its a pretty safe bet that the 6.8 will not dethrone the 5.56, at least for the military.

I would be highly shocked to see any new round for the military until they decide to replace the current platform. Even then, most of the weapons they have seriously looked at have all been 5.56 based

USSR
March 8, 2006, 11:09 AM
Short answer -- Nope. Much as I would like to see a heavier caliber replacement for the 5.56, the 6.8 Rem is DOA.

Don

Bartholomew Roberts
March 8, 2006, 11:32 AM
You can also do a search here and get considerably better information on the 6.8SPC than that article.

Zak Smith
March 8, 2006, 12:35 PM
Welcome to 2004.

Bobarino
March 8, 2006, 02:04 PM
i'd think the 6.5 Grendel is gaining more ground than the 6.8SPC. even Wolf is making the 6.5 now. its long range ballistics are WAY batter than 6.8. i don't think either one will replace 5.56 in the next ten years anyway. i still say .260 remington is the way to go. light, already proven, (against game anyway) plenty of range, tooling already exists, light recoil. but then that wouldn't allow the .gov to waste a gazillion tax payer dollars developing their own goofy proprietary cartridge that costs a ton. silly me.

Bobby

Jack19
March 8, 2006, 02:06 PM
No, 5.56 isn't doomed. (Actually it works pretty well in it's niche.) And it's unlikely that 6.8 will replace it.

rbernie
March 8, 2006, 02:24 PM
i'd think the 6.5 Grendel is gaining more ground than the 6.8SPCI'm sold - where can I go to mail-order a 6.5 Grendel barrel and bolt for an upper that I'm building?

Bobarino
March 8, 2006, 02:27 PM
Alexander Arms seems to be the leader in the 6.5 grendel right now. http://www.alexanderarms.com/

Bobby

rbernie
March 8, 2006, 02:51 PM
Alexander the leader? Heck, they invented the 6.5 Grendel and then kept the cartridge (and uppers and bolts and such) proprietary for over two years. I decided several years ago not to pay for one of their pre-assembled uppers, which is why I'm not currently shooting the 6.5 Grendel.

In recent past, Alexander has reputedly provided certain other vendors with chamber reamers, and authorized additional sources to supply brass and barrels and such. Given your posts, I thought that you were 'in the know' on this and had sources of supply lined up for third-party (affordable) 6.5 Grendel bits.

Sorry for the confusion.

TexasRifleman
March 8, 2006, 02:55 PM
This sounds just like the "10mm will replace the .45" spin when that great round first appeared. There may have been many technical reasons why 10mm was superior to .45, but you just can't supplant one of the most used calibers in the world with a few technical changes and some new gear.

Zak Smith
March 8, 2006, 03:38 PM
but then that wouldn't allow the .gov to waste a gazillion tax payer dollars developing their own goofy proprietary cartridge that costs a ton. silly me.
Anyone familiar with development of the SPC knows this is not true.

Bobarino
March 8, 2006, 03:57 PM
i know, i was being sarcastic.

i'm affraid i don't have any more information on the 6.5 than your average googler. sorry to dissapoint.

Bobby

Dr.Rob
March 8, 2006, 04:57 PM
The Army killed the 6mm option the FIRST (that I know of) time in the early 80's with the development of the SAW (now the M-249), due in part to cross-comapatibility with other NATO nations.

While we can arguably bring our own pop-gun (pistol) to a fight we might have to share rifle ammo with our allies.

Just a thought.

carnaby
March 8, 2006, 06:54 PM
I keep seeing the term "cross section density" used. I don't understand what this means. Anyone care to explain? Which cross-section does it refer to, looking at the bullet nose-on, or looking at its side? :confused:

And how does this change with bullet shape anyway? Aren't the bullets basically made out of lead and have the same density thoughout, except for the jacket? :confused:

Mute
March 8, 2006, 06:55 PM
The 6.8 SPC was not conceived as a general replacement for the 5.56. Some units that had access to the shorter barrel ARs found the 5.56 lacking and wanted something that could resolve that problem without having to replace the existing firearms. After a great deal of research, they settled on the 6.8 SPC. It was the answer to a very narrowly defined problem and it did that quite well. The 6.5 and the 6.8 both have certain qualities that will be beneficial for certain needs. Neither cartridge were competing to be a replacement for the 5.56 either then or now. Edited due to Forum Rule #3 - BR

KriegHund
March 8, 2006, 07:01 PM
It should.

But it wont. Not anytime soon, anyways.

I dunno, they ARE switching from 9mm to .45. So maybe there is hope.

longhorngunman
March 8, 2006, 07:20 PM
Why would you want to replace the 5.56 Nato? It works great for what it was designed for. Remember it's being used on human beings mostly not some tough hided strong animal. Need greater distance, that's what the DMR is for.

USSR
March 9, 2006, 08:27 AM
Why would you want to replace the 5.56 Nato? It works great for what it was designed for.

That's the problem. Design something for one set of parameters, and then along comes a different kind of war with a 'nother set of parameters.

Don

KC&97TA
March 9, 2006, 06:28 PM
cough, cough (I never said this)

Rumor on the 'cool side of the house' says that the guys who have reason for a .45 or 6mm may so be equiped on a wider scale in the future. Riflemen may get thier A4's replaced with a 6mm. The various test .308's are on the streets, shorter shottys, and various 'new toys' are getting to were they need to go. With the demise of the Corps DET-1 we'll have to wait and see where the Kimbers will end up and there's a screeming for more .45's in a hurry.

This distribution has been on a "who rates" so those in the rear with the gear, will keep thier M16A2's and 9mm.

Not everyone is switching to .45acp, just those who NEED it and will USE it

5.56 doesn't do well killing humans when they're doped up on Coke/Heroin-coctail of suicidal intentions

longhorngunman
March 9, 2006, 07:30 PM
Neither will .308 on that scenario.

berettashotgun
March 9, 2006, 08:30 PM
I work for OC-ALC and in one of my many classes on the warfighter I was shocked to hear that troops killed in action have less of a death benefit than a civ fed employee (me). The instructor, retired AF, was disgusted to state this fact. Quote," Where's the outrage?" I think that applies to anyone recieving anything but the best tool for the job in combat. .45's ( or at least .40's) and 260's minimun.

berettashotgun
March 9, 2006, 08:38 PM
Had to add this- it is along the same lines as this thread. My sweetie carries on the job- nothing serious, just guarding snot-nosed brats (well- teenage morons) and teachers from each other. She was originally qualified in a 9mm, so she is required to carry that ROUND- not the pistol she qualified with- a Glock 17. I am proud to say she can shoot ALMOST as good as Annie Oakley after 3k+ rounds each year , but she carries a concealed 45 because she can shoot it alot better( para P-12:cool: ). Now if a female thinks more is better ( get your mind out of the gutter:rolleyes: ) anyone who makes this decision should. There should be no reason to have to explain or justify your reasons for personal safety.

Zak Smith
March 9, 2006, 08:43 PM
Rumor on the 'cool side of the house' says that the guys who have reason for a .45 or 6mm may so be equiped on a wider scale in the future. Riflemen may get thier A4's replaced with a 6mm.
Are you saying there is ANOTHER new assault-rifle cartridge, and it is 6.0 mm ?

Jeff White
March 9, 2006, 09:36 PM
cough, cough (I never said this)

Rumor on the 'cool side of the house' says that the guys who have reason for a .45 or 6mm may so be equiped on a wider scale in the future. Riflemen may get thier A4's replaced with a 6mm.

So we take another wrong turn on the dis-information superhighway so that someone can talk smack about his favorite cartridge or talk down his least favorite....:rolleyes:

Jeff

James T Thomas
March 9, 2006, 10:29 PM
Is it the Swedish round 6,5 X 55? I believe the ballistics and history both of that one would put it in consideration as a better replacement.

Why all the experimentation for something else, unless there is money to be made?

I think that something well proven is at least worthy of a look.

antsi
March 9, 2006, 10:48 PM
--------quote-----------
I keep seeing the term "cross section density" used. I don't understand what this means. Anyone care to explain? Which cross-section does it refer to, looking at the bullet nose-on, or looking at its side?

And how does this change with bullet shape anyway? Aren't the bullets basically made out of lead and have the same density thoughout, except for the jacket?
------------------------

Sectional density is the mass of the bullet distributed over its frontal area.

Think of a dinner plate coming at you, flat side towards you. Very low sectional density.

Think of a crossbow bolt, or the penetrator from a saboted AP tank gun round. Very high sectional density.

More sectional density generally means more penetration.

Given the same caliber, the only way to change sectional density is with a heavier bullet. That's why all things being equal, heavier bullets generally penetrate better if the caliber is the same.

Tony Williams
March 9, 2006, 11:25 PM
For more info on sectional density and its relationship to ballistic coefficient etc etc see this article on Basic Ballistics: http://www.quarry.nildram.co.uk/ballistics.htm

If you're interested in alternative military rifle calibres, you might also find this useful: http://www.quarry.nildram.co.uk/Assault.htm

Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion forum (http://forums.delphiforums.com/autogun/messages/)

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