OT: ? New Government cartridge? 6.8mm

Kismet

Kismet

Joined
Jan 30, 2002
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from Plainsman's Cabin Forum:

I have seen that the US gov't is about top adopt a new round for its military. It is a 270 caliber short cased rimless round that can be used in the M 16 class of firearms. The new round offers a 6.8 mm 115 grain bullet at 2650 fps out of a 16" barrel. Apparently the reason for this new round is that there were concerns over poor performance of the 223 in the deserts of the Middle East.




Comments from the gun-knowledgeable folks?

Thought the .223 problems were action-related, not cartridge issues.:confused:
 
The 223 was always designed for use in a 18 plus inch barrel and a 50 grain ( +/- )
bullet, out of a standard twist rate ( 1 in 10 to 1 in 14 IIRC ).

It's high velocity combined with light stabilization to break the rear of the bullet to pieces when it began to tumble.

It is now used with bullets weighing 65 to 70 grains ( to increase long range penetration ) slowing bullet speed.

Next, they changed the twist to 1 in 7 or 1 in 9 , stabilizing it so it exits before beginning to tumble, and staying together.

Finally, they change to the M-4 with who knows how short a barrel, dropping velocity ( and thus energy ) even more.

Then they complain it's still too long a gun for working in and around vehicles.

Once they change to a new cartridge they'll do the exact same things to castrate the new round.

We still haven't learned from the Spanish-American war where they sent our troops with 45-70 single shots against the 7mm mauser repeater. Of course we couldn't possibly admit our error and adopt the 280 British or the 275 Rigby -
( actually the 280 british was a 284 or 7mm caliber - and the 275 Rigby just another name for the 1891 or 1893 7x57 ).

Over a hundred years and we reinvent the 6.5 Swede and the 7x57, but call it a 270 ( .277-8 bullet rather than the 264 caliber 6.5 Swedish or the 284 of the &x57 ).

Now that's progress.
:rolleyes: :rolleyes: :rolleyes:
 
It's a very hot subject, but generally the 5.56 bullet won't fragment reliably below 2700fps, so wounding below that line is pretty much a .22 hole and that's it. That means M4s are only effective out to 100 yards or so with the new 62gr ammo, before the velocity drops too much. M16s with the longer barrel can keep it above 2700 for a bit longer range. The older M193 55gr ammo has the same characteristics. IIRC Most wound ballistics experts consider the fragmenting 5.56 round to be more effective than the non-fragmenting 7.62 round. But once it does not fragment, it is not very effective.

Since after WWII when the 7.62x51 was finally adopted after a big fight, the alternative was a mid-range cartridge of about .280 size. They're still looking at the same concepts. Personally I don't think the 6.8mm is going to get adopted on a large scale due to inertia and egos... Alot of folks are looking at heavier open-tip-match (OTM) 5.56 bullets, of 68-77 and even 100 grains. These bullets are designed differently and will fragment at lower velocities.

Here's a link to Fackler's article Wounding Patterns of Military Bullets. It has a graphic of the fragmention patterns of the 55gr bullt at various velocities.
 
Rusty beat me by a few minutes. For more info check out ar15.com or the yahoogroups ar15-l mailing list, it's been discussed to death. I do not feel the twist rate has anything to do with the wounding characteristics. In the link I posted, the wound cavities are essentially the same for the two rounds. The only time it comes into play is when the bullet is almost unstable, as in a (rare) 1:14 barrel. The 1:12 twist of the original M16s with 55gr bullets keeps the bullet equally stable as the 1:7 twist does for the new standard 62gr M855 round (SS109). Note you can get this unstable behavior when shooting the 62gr ammo in a 1:12 barrel.

I am an AR15 junkie. I stock 55gr ammo since if it's a meat target past 100 yards or so it's probably not getting shot at... And use a 1:9 barrel so it shoots almost any weight bullet acceptably. (And I don't have any problem with the action either :D)
 
Should note that at the turn of the 20th century, barrels were up to 30" long, and have been shrinking in length the whole century. 22 inches is now standard for non-magnums, and ultralights go shorter.

The french and the brits have gone to bullpup configuration, and with the increase in vehicle use if we want to get any useful velocities we'll have to do the same.

mPisi, thank you for introducing some sanity into my rant. ( Not that it seems possible to contemplate the governments actions and maintain your sanity without psychtropic medication!!! )
 
the 6.8 SPC looks very interesting to me, though I've heard nothing but mild rumors about the army actually looking to change over(including talkign to guy from Barrett, who's making one of the uppers). 115gr bullet doing 2650 fps out of a 16.5" barrel sure intriques me though. Seems to kep it's energy well too. Barrett will start taking orders for the uppers at the shot show,a nd Remington is shiupping ammo now(though expect it to be hard to find for a while). I haven't tracked down anyone selling the new followers needed but sure someone has boxes of them ready to sell.

I'd much rather see us looking at things like this, to improve the M16 system, then going to the XM8/G36 system. Rather that going to a whole new weapons system, including new mags, and all the costs invovled there(especially as the government decided us peons shouldn't have full auto or burst firearms, so can't recoup any of costs of changeover by surplusing out M16s/M4s to civilians), I'd rather we look at improvements to an already refined design. the 6.8 SPC cartridge should definitely get a hard look by the army. Hayes Research will be announcing their gas piston upper for the AR/M16 systems at the SHOT show I believe. I have videos of that somewhere going 3500 rds full auto(Thanks to cav arms, who lent Hayes Research soem of their registered lowers) without a stoppage.

Just hate idea of going to the XM8, and all the costs involved in that, when it's not even an improved cartridge, jsut fires same thing. So you get all new training costs, manufacturing, replacing all guns and mags, to fire same cartridge. If the thing was in a superior cartridge, then I might not dislike the idea so much(though I'm not a fan of HK plastic guns either :) )

But anyways, I'll shut up now, as my rant is quite a bit OT for this forum. :)
 
Forgot. Here's a pic of Barrett's upper(supposed to be nice with suppressor they've got, coruse, we won't get those)

http://members.aol.com/_ht_a/docgkr/myhomepage/6.8mm_Barrett.jpg

Here's the PRI upper on a gun:

http://members.aol.com/_ht_a/docgkr/myhomepage/6.8mm_PRI.jpg

And here's a 100yd 5 shot group from an M96 in 6.8. THis is NOT meant to be an example of one of the uppers, as this is a custom build with one of best barrels around(Mike Rock), but to show capabilities of the cartridge. Also to my mind shows that there's possible accuracy for anyone in this cartridge, as MIke Rock already has the barrels. But anyways, on to last pic:

http://members.aol.com/_ht_a/docgkr/myhomepage/6.8mm_Target.jpg
 
munk, I agree that a .277 at 115gr is not going to be a ballistic dream. I often thought that if they wanted a bullet at that weight they could use the a .257 at a 120 grains, a 6.5mm would be ok too. I'm just guessing, but I bet the reason that a 115gr .277 bullet is the longest that they could fit in the magazine (without seating it too far into the cartridge and take up powder space). If they went to a fatter cartridge to get the powder capacity back then maybe it wouldn't double stack in a stock size magazine. Also, fatter cartridge = more rearward thrust against the bolt. I know that there are a lot of guys making custom uppers using the fatty cartridges ~ but I wonder if this is wise. I haven't measured the size of the locking lugs on a AR, but they might be pushing things a bit.

Best that I can tell the whole tumbling bullet thingy was not a planned mode of operation. It was a result of the switch to heavier bullets without increasing the barrels twist rate.

Adios,
stevo:)
 
I think if they'd gone to a 243 instead of 223 we'd have been better off. They want the larger diameter now but wont give it case capacity because of weight.

Perhaps with some proprietary loading techniques from the big maunfacturers- like Hornadys light mag- the little case can give more.

Someone opined they must pour the powder in the case as a liquid, don't know if that's true.



I think too much has been made of 'tumbling" Our rounds never 'tumbled' in flesh much- it takes many inches of depth to get one started unless you hit bone. Likewise, i don't think any one realized the base was breaking up and contributing to wound cavity size unti much later. I agree we should stay with the 16 model until the next real big step forward occurs. Our mistake was in not offereing two versions, the 18 was gas piston driven and more reliable in sand. Many parts are interchanable. Would of been a good thing.
 
munk, amen on the frag and tumbling ~ you summed up my thoughts better than I could. Anyways, fragging and expanding bullets are both outlawed by the Geneva convention I believe.

Light mag technology is a good idea, give them another 100 fps or so.

There are a couple of folks making piston operated set ups for the AR, ala the 18/180. I don't think it would be that big of a deal to perfect them and integrate them into the current platform.
 
Armalite's released a new version of the 18 called the 180. I'm waitng for the ASSault weapon ban to sunset to see if they'll offer folding stocks again- a plus for the 18 not available for the 16 with its spring mechanism.


But actually there's nothing going on that makes me regret retaining the M1A. I'm currently without an AR sytem but will keep my M1 forever.


munk
 
The cynic in me says we'll reinvent this wheel every 40 years for no better reason than to award another huge defense contract.

I'm not up on the test data here, but the handloader in me says you improve ballistic efficiency in a given caliber when you lean towards the upper end of the weight scale. So a 115 gr .243 nwould make a lot more sense.

Grr, too early in the morning for me to get my mind around this topic, need more coffee.

If this does happen, where do you think all those surplus M16's will go?
 
The '16 family is old technology. Yeah, it work okay, but it could be better, and if we're going to a new round anyway, we might as well scrap the platform.

The 6.8 is more like a 7.62x39mm, except it shoots flatter.

I don't think the 6.8 is the answer, either. What the US needs to do, is go with a smaller diameter cartridge with slightly higher energy than a .223 and high sectional density. The ideal cartridge will be close in size to the 5.56x45mm, but will have significantly higher retained energy at distance. A aprox 6mm bullet weighing around 100 grains, and traveling about 3000 fps should be nearly perfect. A round like this would enable replacing four weapon systems (rifle, sniper or SDM rifle, SAW, and GPMG) with three or possibly two weapons systems, as well as replacing two cartridges with a single cartridge that will work just as well in one role, and better in the other role.

There are arguments against this. Most prevalent is likely the "but we have x inventory" of arms and ammo. So friggin' what. This is the same argument that lead to the problems with the M1 Garand, which should have been a .276 caliber. This type of argument has stood in the way of progress for at least 100 years. Yes, it can be a valid argument, but only if there is no significant advantage to the change. In this case, the Armed Forces are already transitioning to new weapons in many cases (M4, M16A4), and changing to a better overall cartridge (flight performance on par with .308 NATO, size close to 5.56) will ease supply and ultimately, SAVE MONEY. But, let's think short-sightedly...always worked for us in the past. :rolleyes:

John
 
The 6.8 conversion is just an upper, so there won't be any surplus M16s to sell off.

If they adopt the XM8, that would end up with surplus M16s, but they wouldn't end up in civilian hands. You'd get a lot sold cheap to LEOs. You'd get more in warehouses sitting and doing nothing. And rest would probalby be destroyed. Same for the mags.
 
Raghorn, until the next big step is here, it makes no financial sense to refurbish an entire army with a different platform, when the existing one has been improved and works. The military cried for a replacement to the .45, and look what we got.

The Soviets have a rifle that fires both with gas piston and recoil, two rounds in the barrel at the same time with same point of impact- now, that's a step forward.


munk
 
Originally posted by munk
The military cried for a replacement to the .45, and look what we got.
Click to expand...

Okay, not to start any fights here, but the Airforce are the ones who were crying for a new pistol, because the gov. model was too heavy. Of course, the other services said if their power was being cut, they wanted more capacity. Naturally, we couldn't have TWO issued sidearms to fit different missions! So, we have the M9, which is as big or bigger in every dimension, heavier (when loaded) and fits fewer people's hands.

On a similar note, remember the big push for the 10mm for the F.B.I.? Standard caliber got switched from .45 to 9mm, and then those agents got killed by a guy who was hit a couple (not eleven, as the myth has grown) times and managed to wing off a few before he died. This really had nothing to do with the 9mm, it's just that he hadn't bled to death yet. Anyway, the Bureau decided that they needed a new, more powerful round. They couldn't go back to the .45 because they'd phased it out before and that would be embarrassing, so they decided to work in conjunction with Smith and Wesson to resurrect the once-wildcat 10mm and turn it into a service auto. Here was an automatic with ballistics and killing power in excess of the .357 magnum and approaching the .41 mag. Problem was, a lot of the agents couldn't handle the recoil and muzzle blast. So, the cartridge was toned down to a more manageable performance...until people figured out that it didn't have anything over Smith and Wesson's .40 and the 10mm kind of died again.

Funny. I wonder how many millions of dollars they wouldn't have had to spend if they'd just pulled the ol' Colts out of storage. :rolleyes:

Aint government great!
 
T1mpani; I believe Smith introduced the .40 after the FBi tried the 10. One wonders what was wrong with the .41 Action Express, other than the domestic companies fought against it.

munk
 
Dunno if this is pertinent, or relevent...but

long ago and far away, I remember some Army colonel who basically created a wire-guided ground to air missile from parts in the storeroom shelf. At the time, the Army had been spending (literally) millions in direct expense...not counting all the bureaucratic time...working on just that thing. Test firing, drones...etc...big media days... all for naught.

Then this colonel popped up with his model...which met all the criteria and cost (old memory) something like $2,000 a pop, and could go into production immediately.

It made the news...not so much for the efficiency of the colonel's design, but because he was transferred to Antarctica and put in charge of counting ice crystals for the rest of his life.

Systems design seems to be related to Staff Officers "riding" a project to promotion. The Army brass was NOT amused at the colonel's innovative thinking.

But, I'm sure that doesn't happen any more.
 
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