Why not 6.5 mm or 6 mm? Seems to me that sectional density and velocity would favor something smaller than 6.8 mm.

Also, I don't see that 6.8 would offer much over a 75 gr or 77 gr 5.56 mm load, except maybe in the SAW (penetration of light cover being one of the 5.56 mm's failings).

[url]www.guns-weapons.com[/url]

The annual Special Weapons for Military and Police does a comparison on six different 6mm loads.

edited to add: Sorry Don, I feel like an ass. The provided link will only allow you to access the table of contents. Anyhow, it's in the spring 2004 issue, if you are so inclined.

Troy,

I just began looking at the ammo forum, and the only 6.8 threads I've found didn't explain "why". I have heard some talk of terminal performance, particularly related to short barrels. But not a well rounded explination.

because the [b]British[/b] said so ! [NI]


(and Remington)

Much better barrier penetration is a big factor. Here’s an example:

[img]http://members.aol.com/_ht_a/docgkr/myhomepage/556_68AKmag.jpg[/img]

Remember that it is a common practice to carry loaded AK-47 mags across the chest, so this is a very relevant test. The 77gr OTM has better terminal performance on completely unprotected (other than regular clothing) target than the M855 round, but the opposite is true when shooting through various types of intermediate barriers. The 6.8 SPC outperforms both rounds in both circumstances by considerable margins. I’m still trying to find a link to a bare gelatin comparison that I downloaded a while back; I’ll post it when I can find the URL.

IIRC, the 6.8 has also been said to fragment out to 150+/- meters out of 12" barrel carbines and out to 400+/- meters out of 20" barrel rifles.

This while still weighing and having about half as much recoil as 7.62x51 [i]and[/i] having better barrier penetration (than 5.56).

Okay, I can see the benefits of 6.8mm when used in a military/LEO setting where penetration might be crucial.

However, here's the thing -- why 6.8mm in the civilian sector? Other than the cool factor, why does anyone need a 6.8mm SPC rifle? That's not to say that it needs to be restricted, HELL NO. What I am saying is how does 6.8mm perform in relation to more "civilian" activity -- High Power competition, 3-gun, hunting, etc. Does it offer anything more than 5.56mm or .308 in those respects?

Personally, I think 6.8mm is a solution to a non-existant problem. I've killed my fair share of game animals, large and small, with a 5.56mm and with .308. Hell, I've killed a number of 150+ lb feral hogs with a .22Mag. I just can't see replacing or retrofitting any of my existing setups with something chambered in 6.8mm as being beneficial. Existing mags don't really work (a 30-round mag holding and feeding 5 rounds reliably is laughable), ammo is expensive ($13 for 20 rounds), and until the Big Three of AR15s (Armalite, Bushy, and Colt) get behind the cartridge, there aren't any lesser-cost options for changing over.

I guess my hesitance to get behind the round and its touted improvements over 5.56mm is simply hesistance to invest time and energy in another cartridge that does the same thing as any other cartridge -- go boom and kill things!

Jeremy

JC_Conn,

I'd like to respectively submit that you
are missing the primary purpose why we have guns and might be interested in 6.8 if you have to question why "civilans" might want to have these rounds.

The reason some of us need this round is because "they" have them.

Chas_martel:

Your use of the pronouns "we" and "they" is confusing--you did not include antecedents in your statement so I do not know exactly whom you are referencing.

Take off your tinfoil hat and be specific.

If you think that you need a weapon chambered in 6.8mm SPC in order to be on the same playing field as "they", then by all means, do so.

My question was not:

"Why does Chas_martel need a 6.8mm rifle?"

Instead, it was:

"Why do I need a 6.8mm rifle? How does the round perform for what I would use it for (e.g. hunting, markmanship, etc)?"

So, unless you've got a Mk19 Grenade Launcher, an M249, and a closet full o' Tomahawk Cruise missles, "they" WILL HAVE SOMETHING YOU DON'T.


Jeremy

Troy,

I've tried to follow this topic for the last couple of months, but either I've forgotten one detail or it was never made clear:  Do you know if the new requirements and testing protocol specified measurable terminal performance, e.g., max neck length, min crush cavity, min strectch cavity, etc.,  or was it more of a "give us your best effort and we'll test to see which one works best" type of deal?

I know the reason 6.8 was selected was because it tested beter than 6.5, 7mm, 6mm, etc.  However, up until this testing, I don't think Remington made a .277 115 OTM bullet so they had some free reign in designing the most perfect slug possible.  But I also wonder if other rounds tested used essentially existing off-the-shelf bullets that weren't optimized for the requirements trying to be met.  Just curious if you know how this transpired.

Maybe I'm off base here, but in some respects that's how I view the process to get the new 77 OTM loads -- I'm not aware of any changes requested to the existing bullets to meet specific requirements (other than adding a cannelure to prevent setback), it was just a case of load up some Sierras, Hornadys and Noslers and see what works.  

Thanx,

jmart

With the Hollywood bank robbery and the riots in South Central LA fresh in my mind, the value of a round that works well against someone wearing a vest containing loaded AK mags seems clear. From a civilian perspective, even.

And very obviously clear from a military perspective (Afganistan and Iraq come to mind).

I don't think this round will be approved for CMP competition anytime soon. Maybe it will work well in a space gun (match rifle) in NRA Highpower.

Two good reasons:

1. Competition.  It makes the Major Power Factor in IPSC/USPSA 3Gun competition.   Also, it will knock down steel with more authority than 223 at long ranges.

2. Hunting.  A 115gr OTM or 120gr Barnes "X" bullet at 2700-2800fps MV is more than enough for deer-sized game.

-z

Troy,

Thanks for the clarification.  From what I've read so far, the round sounds like a measurable improvement over what's available now.  The one thing though that I've heard,  which in my mind is the main detractor, is the non-compatibility with existing, unmodified AR mags.  But, if they have to come up with a new mag, then maybe they can build a higher capacity one while they're at it.  Going from 30 to 18 is a big reduction.

Ultimately this sounds more like an integration task than a classic design task, given the various constraints they had to deal with as you've pointed out.  I know everyone has their favorite caliber for whatever reason.  Still I wonder if specific terminal ballistic requirements had been specified up front, that other bullet diameters and/or case designs could have tested better since they could have played with jacket thickness and hardness, core hardness, weights, etc. to achieve the desired performance.  Who knows, maybe a smaller caliber and/or smaller case could have matched the demonstrated 6.8 performance, and in the end met some other desirable design goals like mag compatibility, mag capacity, downrange energy, etc.

jmart

If the US Army is going to adopt the XM8, then the magazines will all change anyway since that uses plastic items incompatible with the M16's.

I know the betting is still against the 6.8mm being adopted, but I'm hoping that the XM8 may swing the deal. If the XM8 stays in 5.56mm, then the case for adopting it is weaker; yes, it's a better gun by all accounts, but is it so much better that it's worth the hassle of changing? An XM8 in 6.8mm, though, would be a MUCH better gun!

Tony Williams: Military gun and ammunition [URL=http://www.quarry.nildram.co.uk]website[/URL] and discussion
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Because it's proprietary... to the extent that a very few were already set up to do the case heads and rifling. I'm told that much of the testing was done with a 105 gr. 6mm load based on the 6mmPPC(7.62x39) and only moved to the "improved" 6.8 design after the money moved in.

I suspect that many an armchair general asked the same question about the .223 vs. the .222 "back in the day"

- But that's only an "internet anecdote"

I'm thinking that somebody gave up on the idea of controllable full-auto fire but other that that, I like it.

It has been my long experience that when anyone uses this phrase regarding nearly any topic, what it really means is
"I don't personally believe I need one, so I don't understand why ANYBODY would"
and/or
"I don't like change/innovation, and I want to argue"

"Need" is a relative term.  I don't "need" all the firearms I have, but I sure as hell won't be heard saying "owning 3 ARs is a solution to a non-existent problem, so why would anybody have them?"

And lastly, you CAN kill a deer with a .22, but it is a better bet with a bigger bullet.  I wanted the 7.62x39 to deer hunt with before this came along, so now I'm waiting patiently until things get rolling and I can build my own 6.8mm Remington "Deer" rifle.

NOC:
To the best of my recollection the 6mm on a 7.62x39 case was never even considered-the 6mm wound ballistics from what I have seen have never been too impressive-The first choice was 7.62x39 on M4 but due to some compatability issues was not able to be done. The new case (actually an old out of production case) was selected due to many constraints and a bullet larger than 6.8mm was originally tested and considered-and then all calibers from 6mm on up were tested and 6.8 was the best compromise between accuracy, velocity, pressure, bullet diameter and weight, wound ballistics and compatability w/the M4 platform.....quite a bit of thought put into it actually.  

1)JD Jones was talking about this concept before 09/11. The systems being pitched currently are a result of 10-20 contractors making committee based decisions about their bottom line. If you want to pretend that this is something other that the truth... no skin off my ass.

2)Unlike others, I'm not going to pretend to be the voice of the "guys in the field" but I would rather have a system based on the MK 11 - but then we would be excluding the politics and the gee whiz factor of a new case head and bore diameter.  

Remind me again... Why 6.8?

Because it will be cheaper than existing systems with better ballistics? (nope)
Off the rack replacement parts? (err if you happen to break a lower receiver)
Because it will weigh less? (man I'm sure that the 2-6 oz. will make all the difference)
Because it's more controllable? (mmm kay I'm beginning to see a pattern here)

Are we comparing apples to apples here? MK 11 Mod0 without a comp and the 6.8 SCAR proto without a comp... which one has less recoil? Have you actually shot either?

Didn't think so.

Back to apples to apples... The comparative weights of the Robinson SCAR-L and the Barrett SCAR-L (the misnomer of the "L" being for light) when compared to the MK 11.

Have you done your math here?

Didn't think so.

On to cost... heh :D

/*edit*/
Size? Car version of the MK 11... nuf said?
/*edit*/

Ummm yeah. Guess I'm just a pinhead singing the praises of something that I've never seen and don't know a damned thing about.  

From the ballistics info available it sounds like they have upgrade an AR-15 from a varmint class rifle to a a rifle suitable for deer.

This seems like a good upgrade.  A good excuse for everyone to buy a new upper.

NOC, if you don't want one, don't get one. don't, however, tell everyone else here that they shouldn't get one, either.

Nick (gonna build one, so there!)

Here's another way to look at recoil.  Anyone who spends any time trying can learn how to shoot rifles and not be bothered by the recoil impact -- even with 308.  This isn't a macho thing, it's just that you learn how to hold the gun such that it doesn't hurt you.  So I conclude that the conventional way of looking at recoil: how much it hits you, is not particularly useful.

For anyone who shoots in an action context in which fast followup shots, repeated engagement, double-taps or controlled pairs are required (this would include IPSC/3Gun, hunting dangerous game - maybe large feral hogs, and I presume combat), sight picture disturbance during recoil is a much more relevant aspect of recoil to care about.  

If your sight picture doesn't move or moves less, you can do faster double-taps and/or at longer ranges without re-aiming.  Your controlled pairs will be faster and faster at longer ranges.  Most target-target transition will be faster because the gun didn't move off target (or didn't go the direction you wanted).  In all of these cases, re-acquiring the sight picture for the next followup shot will be faster if the gun moved less off-target during the first shot.

The first aspect of recoil is the actual impulse from the bullet and gasses exiting the barrel.  A good compensator (or even a suppressor) can capture that gas momentum and harness it to reduce the impulse.  Not much more you can do there.   The next aspect of recoil will be the bolt bottoming out to the rear in the stock, and finally, it will come forward under spring force and slam into battery.

Consider those events in light of (1) how much force acts on the gun when the bolt carrier assembly hits the rear, and then slams into battery, and (2) how long it takes for all those events to happen: from ignition back to battery.

Each of the bolt carrier impact events will upset the gun, and further disturb the sight picture.  The most important factor here is the mass of the bolt carrier.    The AR10 bolt carrier is MUCH heavier than the AR15 bolt carrier assembly.  This aspect of recoil is much worse in an AR10 than an AR15 for this reason.      As a corrolary, this makes 6.8SPC (in an AR15) disproportionately better than .308 (in an AR10) in terms of recoil disturbance- it's got less reciprocating mass by a long shot.

-z

NOC:
I am speaking of the 6.8mm as it sits from the program it sprouted out of. I am aware of some other peoples' and countries projects.
Yes, also J.D. Jones was interested in the program also (He contacted certain people in the program well before anyone here had heard of it). The program for what later became the 6.8 started a bit before 9/11 also. I remember the planning stages a few years before it.
There may have been concurrent designs going  but I myself never followed them other than in an academic interest. I am unsure of what has been going on as of now with the 6.8 (been out of the loop for a few months now) but if you want to talk the design of the 6.8x43mm as it is right now, get your facts straight. (If you know so much: what program did it sprout from? caliber?(s?) of the forerunners to the 6.8 then in ? and ctg case dimensions of the prototypes? how many were made? who made them? who tested them? Who was consulted? what magazines were used?)inquiring minds would like to know (maybe the information I have gotten is incorrect-it sometimes happens).
So what are you saying then? It is apparent that you don't like the 6.8 for whatever reason (hey, it's a free country and you are welcome to your opinion) but it seems you don't welcome the opinions of others and nothing can change your mind otherwise-(as I said it is a free country)

If not 6.8mm, what then to meet the(your) criteria? I'd like to know your thoughts. There is no one cartridge as far as I can tell that meets all the demands, but I think (that's my opinion) that the 6.8mm is an improvement over the 5.56mm for reasons already stated.
Did it ever occour to you that perhaps people work with what they've got at the time and it is possible something better will come along if not COTs....but if you never make a decision then guess what? change never happens. The AR-10 came out too late but was more than likely a superior weapon to the M14 but the decision had already been made and money spent. And some people lament.

Have you ever fired a 6.8mm? Just curious

KMFDM:

The perceived need is for something that hits harder and further and there's systems that fit that need better that SPC/SCAR. Nobody even bothers to deny it! (thus my gripe)

Is Remington actually producing production 6.8 SPC yet? If so, where can I purchase some? [:D] I can't imagine that the pre-production "gun bunny" samples will much resemble the rollout. Did you see that contaminated powder? ((shudder))

... Mostly, my frustration stems from watching people hype non-existent products over the past few months.

As a child, I remember reading about some of the guns in the ACR project. Words like hit probability and ergonomics figured prominently into articles with spacey looking devices that hurled darts and multi-part projectiles. What ever happened to "the ACR" anyway?

As an aside- I figure that somebody with your background might be interested in the practical application of commercial 5.56 rounds in Iraq these days. From what I hear, most COTS varmint ammo will drop "insurgents" like a sack of shit.

I apologize for the rambling post – it's 04:00 and I'm out of coffee    

The preprod ammo I've got isn't really that bad.  Certainly not "match" but it runs consistently, though slow.

The practical result of the bad powder is that the MV is about 2700fps, stddev 32fps, and accuracy is around 3-4MOA.

-z

NOC:

My background unfortunatly is not that extensive, I have just learned a few things from alot of people more knowledgeable than myself.
Also the 5.56mm stuff out there that I have seen is in various states of use and or legality. The 77gn was only intended as an interim fix until something better (i.e. new cartridge in larger caliber that could work on the existing "platform" reliably and at what was intended as a low-cost replacement. unfortunatly, some companies that are tooling up to make them want to charge exhorbtitant prices to the gov't)(sorry I use parenthesis way too much here). The RBCD bullet (aka Varmint bullet), last I heard DA JAG had ruled against usage of it in combat due to it's expansion and not 100% X-rayable.
As for the SPC/SCAR yes, there are probably harder hitting variants but in what caliber? the only thing that I have seen thus far that was promising is in 7.62x51 and it is a pain to carry a large quantity of it for everyone in a team or a squad.
The ACR was unfortunatly more than likely some engineers 87 million form of lab-welfare pipedream of a re-hash of the SPIW project from the 1950's. Which I am glad never was adopted in the assault rifle world.
 

No. The first aspect is when the bullet leaves the cartridge. That's why, in general, more powerful rounds tend to be less accurate.

Also, in NRA Highpower, less powerful rounds tend to dominate these days. This is true even in the long range slow fire matches, where 5.56 gas guns have been beating 7.62x51 gas guns, and match rifles with numbers like 6 mm and 6.5 mm have been doing well. I don't think this is as much due to intrinsic accuracy as it is to the ease of maitaining a good position with light recoiling rifles.

DonS,

I agree.   The "reaction" starts as soon as the bullet starts movement.

-z

OK now: who produces barrels, bolts, and magazines for the 6.8?

for me its more a mag issue, if the ban does not sunset, new high cap mags will not be avaliable to me

Having shot the 6.8 on full auto, I do not believe the average SWAT cop or Soldier will find it controllable.  Certainly no where near as controllable as a 5.56mm M4 or 9mm MP5.

5.56mm case necked up to 6.5mm.  Would use existing mags and bolt, requiring only a Brl swap.

I would have thought that 7mm T/CU would have been a good choice.  Not as "hot" as 6.8mm SPC, but would have given you more punch than 5.56mm

That's basically a 6.5 TCU or JDJ, something like that.  Unfortunately, the 5.56 case doesn't have a big enough boiler room -- velocity would be off several hundred fps given equal bullet weights.  Performance at 300-400 meters would be very iffy and trajectory wouldn't be that hot.  

I could see a bigger case with a rebated rim so current bolts work.  But I can't see how designers are going to get around the mag issue.  Unfortunately, that's the price you have to pay to upgrade.

Also in the terminal ballistics department the 6mm and 6.5mm were found quite wanting. Also I am not fully sure existing magazines would work reliably with the 6mm and 6.5mm especially during F/A and burst firing but maybe I am incorrect. I don't trust rebated rims for anything going into combat myself.

Anyone looking into a bolt gun in the 6.8?
I am thinking DEER, what do you think?

Why not .308 ???  how many spares are you going to have laying around for your
6.8mm?  How much 6.8 ammo are you going to get off a corpse carring another AR15 ??????

i'm sorry but 77gr sierra match king bullets are going to pimp out any of an m4's lack of power...  i think 6.8 is the biggest mistake that our army is currently pursuing... its 77gr 556 and gameking's for 308... nothing more is needed... well 50cal

Quoted: i'm sorry but 77gr sierra match king bullets are going to pimp out any of an m4's lack of power...  i think 6.8 is the biggest mistake that our army is currently pursuing... its 77gr 556 and gameking's for 308... nothing more is needed... well 50cal

Those US soldiers who scored seven solid body hits on an Iraqi with Mk 262 rounds only to have him kill two of them might disagree with you about the adequacy of any 5.56mm round.

The 6.8mm was developed at the request of SOCOM because of dissatisfaction with the performance of the 5.56mm - and they probably have more direct experience of shooting people with this round than anyone else.

As for the argument about being able to find spare rounds on the battlefield - if that had always been used against adopting a new round, we would still be using muzzle loaders.

Tony Williams: Military gun and ammunition website and discussion
forum

full-clip, I'm with you.  I read an article in one of the gun mags that I got, they rebarreled a cz 527 for 6.8.  He said the deer went on its back with it's feet in the air at I think it was 90 yards.  But I'm thinking way less recoil than a .308 yet more effective than a .223 what's not to like.  I think NOC should drop the c and add a b.  What have you got to lose?  Plus this loss of 12 rounds someone mentioned is wrong, I believe.  I think the 30 round mags only loose two or three rounds.  Not 12.  I could be wrong but I think that's the case.  You all should read the soldier of fortune magazine.  They tested it and found it to be accurate and worked well.  I think they reloaded some though because they we're using the hornady vmax, or maybe that was that other article about the cz.  Well regardless.  It's being tested.  In several configurations.  Maybe NOC knows something the rest of us don't know.  I don't know.  But from what I've read it seems to me like a great idea.  I think the 77 grainers are a great idea too.  If they do adopt the 6.8, it's not like all our troops will get one asap.  Issue them the 77grainers for now and we can learn more about that while we're at it.  It's not going to be a 1 swipe fix it move.  In my opinion.   Well, blast away!!!!!!!!!!!!!

I've handled the 6.8 in several versions, seen the gellatin and accuracy tests from within house.  Unfortunitly, still waiting a chance to shoot one between deployments.  I would love to have a 6.8 upper for my personal AR for deer hunting.  The land I hunt on has a mim. diameter of 6mm for deer.  Current mag prototypes that I've handled do hold 28 rounds of 6.8 in a 30 rd 5.56 package.

No small arms bullet is so magical that it will drop a human with one shot every time.  Troops that have that expectation have been playing too many video games.

Quoted: No small arms bullet is so magical that it will drop a human with one shot every time.  Troops that have that expectation have been playing too many video games.

Absolutely - it's a question of percentages. If (to take a more or less hypothetical example) you were given the choice between a rifle which would drop the enemy with a solid body hit 50% of the time or one which would do it 25% of the time, which would you rather have?

Tony Williams: Military gun and ammunition website and discussion
forum