An end to the 6.5 vs 6.8 debate.

[Kevin23]

I did not produce this information, but I had been thinking about this for some time, and I found out that Stanc from 65grendel had the same idea. This is the information he put together for the 6.5 GPC. I would like to get some input from some of the experts here on what you think.

"Okay, I may take fire from all sides with this idea, but here goes. I've long thought that both 6.5 Grendel and 6.8 SPC have undesirable characteristics insofar as a .mil application is concerned.

Although 6.5 Grendel can use high-BC projectiles, I'm uncomfortable with the 30-degree shoulder and large diameter of the case; plus, there is also the incompatibility with the M27 link configuration. OTOH, 6.8 SPC case dimensions are compatible with the M27 link design, but the round is handicapped by low-BC bullets.

So, it seemed logical to me that a better idea is to combine the best features of the 6.5 Grendel and 6.8 SPC into one round: the 6.5x42 General Purpose Cartridge.

If the SPC case is necked down and shortened to 42mm length, it can accept the Norma 120gr FMJ. The only difference is that a cannelure would need to be relocated farther forward than for use with the Grendel case (as shown in the attached photo).

As I understand it, for the same bolt thrust the 6.5 GPC chamber pressure can be significantly higher than that of 6.5 Grendel. I figure that'd offset the reduction in powder capacity caused by bullet intrusion. If not, then reduce bullet length to cut weight to 105-115 grains, and boost muzzle velocity. Make the boattail longer to gain back some of the BC lost by reducing weight.

Obviously, 6.5 GPC wouldn't be able to use the longer-ogive bullets that can be put into the Grendel case, but it might be a more optimum alternative than either 6.5 Grendel or 6.8 SPC.

With this bullet, 6.5 GPC performance -- muzzle velocity and external ballistics -- should at least equal, if not exceed, that of 6.5 Grendel."

-stanc

 

[R.W.Dale]

With this bullet, 6.5 GPC performance -- muzzle velocity and external ballistics -- should at least equal, if not exceed, that of 6.5 Grendel."

I think not. Especially with that much bullet intruding into your usable case capacity. This wildcat suffers from the same problem SPC does, too long a case to make the best use of the projectiles advantageous to the caliber. This new cartridge will actually have LESS case capacity than 6.5g because it's smaller in diameter but the base of the bullet is still in the same location. Just like my 30HRT or .30spc actually has less case capacity than 7.62x39 with a bullet seated to the same magazine limiting COL

Honestly I'm getting tired of these long winded mental masturbation posts about the perfect military cartridge by folks who have no combat or even experience in ballistics. Where the entire premise is hypothesis with no loaded ammo sent downrange.

Bottom line 5.56 kills the crap out of people shot with it. That's why we've used it longer than any other main issue service rifle cartridge. You can only make something so dead so what does this cartridge bring to the table?

If not, then reduce bullet length to cut weight to 105-115 grains, and boost muzzle velocity. Make the boattail longer to gain back some of the BC lost by reducing weight.

Sounds like another cartridge....what's it called 6.8 something????

 

[Float Pilot]

Honestly I'm getting tired of these long winded mental masturbation posts about the perfect military cartridge

Brother Krochus
I find myself in agreement with you regarding the 5.56mm, 6.8 and 6.5 Grendel debate.....
However, we should remember that at more than one time in the past, others said the same thing regarding the 45-70, 30-40 Krag and 30-06 /308. They too, killed the crap out of whatever was shot with them..
And yet somebody sat around and developed the 5.56mm. Probably starting with a design drawn on a cocktail napkin in an airport bar...

 

[Shadow Man]

No matter how much you tweak a round, your never going to be able to come up with a round/weapon combination that handles CQB one instant and 800+yd sniping the next. The 6.5 Grendel was desiged for a higher BC than current AR rounds, and the 6.8 SPC was designed for increased barrier penetration and lethality out to 500 yards. Trying to combine the two of them will only sacrifice somewhere important.

Honestly I'm getting tired of these long winded mental masturbation posts about the perfect military cartridge

Couldn't agree more. To do more than one task to perfection, you will need more than one weapon and round. There is no "perfect cartridge."

 

[Jaws]

Actually an even better version has been done before. The 6.5x42mm Czech. If you extend the AK case to 42mm and reduce a little the case taper, instead of shortening the 6.8Spc, you get more case capacity and don't loose that much due to seating the bullet deeper.

 

[Mr. T]

6.8 SPC is not bringing that much more to the table in knock down power when you compare it to the heavier hollow point loads that our troops are employing in the field -- the difference between 6.8 SPC and enhanced 5.56 NATO is very insignificant...definitely not worth the shift in our military to turn away from 5.56 NATO. 6.5 Grendel probably has it's applications for snipers or dedicate marksmen, but it's not a General Issue round at all for reasons already previously stated.

 

[BWB]

As pointed out above, the object of a military cartridge is to kill the crap out of the enemy. But you have to get to him to do it, and 5.56 failures on thin skinned vehicles and windshields/windows/mud or block walls,etc. are common enough to be a legitimate concern.
The answer? About the time we figure that out we'll be back in a filthy steaming jungle somewhere and all this neat electric/optical stuff we have now won't work, and the new basic infantry weapon will be too heavy and unecessarily powerful (?) for the limited ranges involved.:banghead:

 

[Z-Michigan]

Meh. Another OK idea, but completely irrelevant unless you have the resources to get this engineered and into production at a reasonable price. 6.8 SPC has decent resources behind it and is still too expensive (not quite double the cost of quality .308 FMJ) if you don't reload.

heavier hollow point loads that our troops are employing in the field

Some lucky guys under the SOCOM umbrella might be getting Mk262, but I don't think anyone else is. However, real soldiers fighting for the US in the last 7-8 years don't seem to have much complaint with the M855.

 

[hammerklavier]

I may be wrong on this, but it is my understanding that in the original military testing, they did test a 6.5, 6.8 and some other calibers. The 6.5 they tested must be similar to what you are proposing or another wildcat that has been done. The 6.8 won out in those initial tests because 1) they don't care about performance past 500 meters 2) it had the highest lethality. Whatever lethality means, and however it was measured is something 6.5 didn't have enough of (sounds a little ridiculous, doesn't it?).

Anyway, it looks like 6.8 will never be for other reasons, not the least of which is that the 5.56 seems to be adequate, as long as you give the troops enough ammo.

 

[MJR007]

Ok, this is what I think...............................................

My kids love the 6.8spc and their deer hate it.

This is old.

 

[Eb1]

Quote:
Honestly I'm getting tired of these long winded mental masturbation posts about the perfect military cartridge
Couldn't agree more. To do more than one task to perfection, you will need more than one weapon and round. There is no "perfect cartridge."

And yet you clicked the link free willingly.

 

[Float Pilot]

you will need more than one weapon and round. There is no "perfect cartridge."

Exactly..

When you take a fast small bullet designed for a 20 inch barrel (which would have been considered carbine length at the time) and then fire it out of a short 14.5 inch barrel something has to give.

During WWII and Korea troops had multi weapon / cartridge layers for varying circumstances. Sub-guns and M1 carbine for building searches. M1 rifles, 30 cal and 50 MG for open or mountain terrain.
Of course they now issue us so stinking much gear to wear, that you can hardly hold a pistol much less properly shoulder a real rifle. Its like lawyers are in charge or something...oh wait...

 

[Tirod]

The overall load of the combat infantryman is still about what it was in WWII. We've just redistributed the priorities and came up with new stuff.

The basic error some make in trying to determine 6.5 or 6.8 is losing sight of what they were designed for and then misapplying them to the other situation. Trying to make one cartridge do both isn't the answer, it's more like asking why can't we all get along?

Preying for whirled peas isn't on my to do list.

As for the 6.8 bringing more to the table, the bottom line is that 5.56 hasn't been killing crap out of the people shot with it, especially from a 14.5" carbine. AS NOTED a cartridge designed to fire out of a 20" barrel will leave something on the table if it's shot out of a 14.5". It was a specific complaint noted by troops in combat that they wanted more knockdown power. They don't get it from issue ammo, and not all ammo issued is the latest greatest. Special heavy hollow points go to those who need them. They are not general issue.

6.8 was specifically designed to do that with short barrels. With the correct chamber, not the screwed up version Remington introduced, it can and is. Check the ballistics out - military load to military load. Yes, the 6.8 is loaded to mil spec, ammo has been made, and is in the field being tested.

I really doubt the average soldier will ever get either round. Logistics and politics in DC are bigger issues. At least when I get to shoot it, 6.8 is available, and it is just as cheap as civilian hunting ammo. In fact, cheaper than the last box of .30-30 Leverevolution I bought.

Items like that are the issue that I want to bring to the table - the huge amount of ignorant, misleading, and nonfactual commentary that seems to constitute most discussions.

In this case at least the OP got his facts right even if the outcome is less than feasible. As for the rest, I've tried to correct that.

 

[deadduck357]

Another proposal would be something with higher velocity and magazine capacity than either the 6.8 and 6.5, larger diameter projectile and more energy than the 5.56 .

6.2mm OCC http://thehighroad.org/showthread.php?t=498256

 

[Float Pilot]

I had even considered necking a 6.8mmSPC down to 6mm to see if it could push a 80 or 85 grain bullet at 3,000 to 3,100. But it looks like the 6mm WOA did just that and it did not produce the velocity I was thinking about.

Actually the experiments from the early 1960s,, with necking a 5.56mm up to 6mm (6x45) was a halfway nice round. I know some guys who re-barreled mini-14s and use it for northern (arctic) caribou...

 

[Hatterasguy]

I don't like these oddball rounds. Reminds me of the .45 GAP round or whatever it was called.


They are popular for a bit, than disapear and good luck finding them. I stick with commen rounds.


I almost bought an LWRC in 6.8 but thankfully I slept on that purchase, I'm going to wait until NATO adopts 6.8 to buy a rifle in that caliber.

 

[deadduck357]

I almost bought an LWRC in 6.8 but thankfully I slept on that purchase, I'm going to wait until NATO adopts 6.8 to buy a rifle in that caliber.

D.O.D. looked at it and decided against the 6.8

 

[Jaws]

D.O.D. looked at it and decided against the 6.8

It had nothing to do with it's capabilities.

 

[deadduck357]

It had nothing to do with it's capabilities.

Major factor was lack of velocity .

 

[HorseSoldier]

the heavier hollow point loads that our troops are employing in the field

Having handled and shots a whole lot of Mk 262 before I ETS'ed, I would like to point out that it isn't a hollow point round. People seem to misunderstand what an OTM bullet is pretty frequently, but it's not a hollow point, just has a pinhole sized opening at the front end because the case is rolled back to front instead of front to back like a conventional FMJ round.

 

[Jaws]

Major factor was lack of velocity .

6.8 doesn't lack velocity. Actually it has higher MV than 6.5G. Is just because of more aerodynamic bullets available, 6.5 Grendel loses less velocity. But this is only noticeable at longer ranges (over 500m).

 

[deadduck357]

6.8 doesn't lack velocity. Actually it has higher MV than 6.5G. Is just because of more aerodynamic bullets available, 6.5 Grendel loses less velocity. But this is only noticeable at longer ranges (over 500m).

Not disagreeing, just stating DOD report.

 

[HorseSoldier]

Wasn't velocity, it was all about logistics.

 

[Tirod]

Link to the DOD report?

 

[mshootnit]

close but no cigar.