6.8 SPC, 6.5 Grendel, .265 1*, etc.

[Zak Smith]

Just a few nits to pick with regard to terminal ballistics.

Because its basic loading is light for caliber, it launches at a fast initial velocity. This speed is important to fragment the bullet.

What's behind this statement? Unless you have characterized the terminal effects as a function of velocity, I don't think you can conclude this. You seem to imply that a particularly fast velocity is required for fragmentation.

I would be interested to compare magazine capacity between 6.5 and 6.8. Do you know?

If both bullets hold together, the laws of physics (which can't be defied, Captain! ;-)) say a higher sectional density bullet will penetrate better than a lesser one at equal velocities. Now penetration depends on both velocity and sectional density,

That's a really big "if"! On the one hand, we're depending on velocity to fragment and expand the bullet, but on the other hand we want penetration. If the bullet fragments and doesn't stay together, I doubt the original sectional density will have much effect on penetration. If the bullet doesn't fragment and could actually take advantage of more sectional density, that means the impact velocity was pretty low. I maintain my previous position that without actual calibrated ballistic gel tests, we don't really know what would happen.

I also take issue with the PDF ballistic chart. It contains errors: The MV for 6.8SPC from an 18" barrel is 2800fps. The BC of the 115gr .277" OTM bullet is 0.365". The MV of 147-150gr 7.62NATO is 2700fps from a 20" barrel, not a 24" barrel. I'm willing to accept the 77gr 5.56 velocity just because it is so variable: I get 2650 from my 20"'s using Black Hills Blue Box 75gr, but lots of High-Power shooters get 2750fps with those bullets from a 20" barrel, and the Mk262 77gr is allegedly a little hotter still, from a 20".

My second complaint with the ballistic chart is: Who cares about 24" barrels ?! The whole purpose behind 6.5 and 6.8 is that it runs in AR15's, M4's, and M16's. The vast majority of AR15's have a 20" or shorter barrel, and M4's are down at 14.5". Some more specialized carbines are at 11.5 or 12". If you want a long-barrelled long-distance rig, you can get a bolt rifle or an AR10 chambered in .260Rem or 6.5XC.

The biggest problem I see with 6.8SPC is the OAL issue. Few of the current selection of heavier .277" bullets can be used, and even if bullet manufacturers step up, they will ultimately be limited by cartridge and bullet OAL. If not for this issue, I would expect 6.8 to be more versatile than 6.5, like how .260Rem is more versatile than .243WIN, or .308 is more versatile than .260Rem. More cross-sectional area equals more velocity for the same mass, without increasing pressure.

Given the external ballistics, 6.5 has it all over 6.8 past 500 or 600 yards. I question if we care, however. The two applications I see are punching paper and military/LEO sniping at humans (as opposed to material). Neither of these two require an AR15 platform, though it would be a nice option, admittedly. If I'm going to shoot unknown-distance targets beyond 700 yards in the field, it's going to be with a bullet with a BC over 0.600 and a MV of over 3000 (in a gun weighing about 12 lbs, and a big NXS on top).

regards
Zak

 

[DavidZ]

Zak and John,

You two are 'way over my head. I wanted two things, when I finally decided to spend $2500 on a "varmint" gun: to start doing serious target shooting out over 500 yards, and to hunt deer and hogs with my expensive new toy, so at least we could eat some of the produce of the new toy.

I have a Bushmaster Varminter, with which the kids and I have had a lot of fun, but I couldn't think of shooting a deer with it, though little hogs have been no problem. I then found that I could shoot reasonably well out to 400 yards or so, and wanted to go farther out.

I have 400 rounds of factory loadsd and 1000 cases of brass coming for my new Grendel, and soon enough I'll learn what it can an cannot do, but I'll never get into the fancy gelatin-and-physics like you fellows. I do know that I'll go get a mule deer in Colorado next year (or at least have confidence trying, with a 140grain hunting bullet) even if he's at 350-500 yards. With the Grendel, after a good deal of practice, I feel confident in that.

I should think our kids in the Middle East would feel a helluva lot more confident carrying a Grendel versus their mouse guns, too. At 600 yards, the 6.8 is almost a carbon copy of the .223 and that just won't do, thank you very much (our son ships out one week from tomorrow). I wish like anything that they could have Grendels in hand, ASAP; I know that's not the reality of the U.S. military, but I just am not sold at all on the 6.8 for deer hunting or for protecting my son's life.

I know that's a simple-minded way to look at ballistics, firearms, etc. -- but it's where I live, anyway.

 

[TX65]

Regarding the ballistics chart,,,,

- Remington reports the ballistic coefficient of the .277 115 grain OTM at .340 not .365, they also report a MV of 2800 fps from a 24 inch barrel. Since Remington is producing the ammo, I will defer to their reporting. As a note, Jeff Quinn posted earlier his independant test of the Barrett at 2613 fps from a 16 inch barrel. Charlie Cutshaw also reported similar results in an article he wrote. Are you stating the same ammunition gains almost 200 fps from an increase of 2 inches in barrel length?

- The data for all cartridges is based on a 20 inch barrel, take note of the legend on the bottom of the chart linked to earlier in this thread. Yes, there was a chart from February that posted all data for 24 inches barrels, this was done to directly report based on Remington's data that was in a 24 inch barrel (As a note, a key person at Remington had no issue with such reporting when he read it at the SHOT show and he could of professionally mentioned this during a rather length and professional discussion)

- The 77 grain bullets run at a nominal 2750 fps from a 20 inch barrel. Nosler reports the 77 at .340BC. While a 75 grain bullet is similar in weight, it is a different bullet.

Is the 6.5 Grendel the ultimate choice for 1,000+ yard sniper duty?,,,no (I would prefer a .338 Lapua Magnum with 250-300 grain bullets for 1,000-1,500 yard duty)

Does the 6.5 Grendel provide a performance advantage over 5.56 and 6.8 at 800m,,,yes

Does the 6.5 Grendel provide a performance advantage over 5.56 and 6.8 at 500m,,,yes

Does the 6.5 Grendel provide a performance advantage over 5.56 and 6.8 at 300m,,,,,yes

Will the 6.5 Grendel deliver this performance in an M16A2,A3or A4,,,, yes

 

[MLC]

for the sake of being redundant

If it hasn't been said in so many words yet I'll take a stab here.
I think that the 6.8 is best suited for military applications or for people, like Zak, that can see a practical application for it.
I believe that for 75% of the interested parties on THR the 6.5 Grendel is the best choice. It has an award winning parent case like no other(6PPC), perhaps the .223 has the second best pedigree(.222).
It has a decided advantage in component availability and potential accuracy IMHO.
For ranges over 500 yards/meters it is unchallenged in trajectory from an AR platform.
In my opinion it is an ideal long range target/varmint cartridge to use in a standard AR receiver.
The biggest issue that has been brought up is reliable feeding and OAL.
This issue is huge for the military application of any magazine fed cartridge.
I haven't seen any reports on how the 6.5 Grendel feeds on auto in an M4 platform nor do I expect to.
The only head to head comparisons I've seen are questionable ballistics charts that show the dominance of
long, slender high BC bullets over shorter lower BC bullets which is really no surprise.
The 6.8 was designed from the ground up to be a CQB to intermediate range cartridge.
The 6.8 is not meant to be the premier CQB to long range sniping do it all in one shot round of the 21st Century.
It is meant to enhance the lethality of issued rifles, mainly M4's, at conventional combat ranges.

 

[Zak Smith]

My mistake on the B.C. I thought I read 0.365 somewhere a while back.

they also report a MV of 2800 fps from a 24 inch barrel. Since Remington is producing the ammo, I will defer to their reporting. As a note, Jeff Quinn posted earlier his independant test of the Barrett at 2613 fps from a 16 inch barrel. Charlie Cutshaw also reported similar results in an article he wrote. Are you stating the same ammunition gains almost 200 fps from an increase of 2 inches in barrel length?

Yes. I have information from a person who has been loading 6.8SPC for about a year. He says that USPSA Major (320) PF is possible with the 115gr bullet from an 18" barrel, which means it's got to be right around 2790-2800fps.

The data for all cartridges is based on a 20 inch barrel, see note on bottom of chart linked to earlier in this thread. Yes, there was a chart from February that posted all data for 24 inches barrels, but it did the same for all.

I was looking at the link Grendelizer pointed to.

The 77 grain bullets run at a nominal 2750 fps from a 20 inch barrel. Nosler reports the 77 at .340BC. While a 75 grain bullet is similar in weight, it is a different bullet.

I don't know what you're getting at. I am aware there are several 75 and 77gr bullets (not to mention the 73gr Berger). Depending on the particular load, they will launch somewhere between 2650 and 2800fps from a 20" barrel.

Does the 6.5 Grendel provide a performance advantage over 5.56 and 6.8 at 800m,,,yes
Does the 6.5 Grendel provide a performance advantage over 5.56 and 6.8 at 500m,,,yes

Quantify performance - not saying I disagree, but without defined terms the discussion would be pointless. Terminal energy is not a reliable predictor of terminal ballistics, especially when comparing different bullets and calibers.

Does the 6.5 Grendel provide a velocity advantage over 5.56 and 6.8 at 300m,,,,,yes

M855 is still travelling at 2262fps at 300m. If we wanted the best velocity, we'd choose 55gr 6mm bullets at 3800fps, but that's probably not the best for killing large beasts. You get my point.

Will the 6.5 Grendel deliver this performance in an M16A2,A3or A4,,,, yes

That's the crux of the matter. It will only if it is adopted into the M16A5. If it isn't adopted by military to any extent, then it is relegated to wildcat status like the many other nonstandard calibers in the AR15 platform.

-z

 

[Zak Smith]

If it hasn't been said in so many words yet I'll take a stab here.
I think that the 6.8 is best suited for military applications or for people, like Zak, that can see a practical application for it.
[...]
The 6.8 was designed from the ground up to be a CQB to intermediate range cartridge.

Very good explanation MLC. The only thing I'd add is this, which I alluded to over in this thread: "The plastic, no-account M-16 rabbit shooter that our Army warriors have painfully. "

We could debate the advantages and disadvantages of 6.5 vs 6.8 all day, but in my opinion, it would be irrelevant.. unless one of us can convince the Army / NATO to change their mind. The one that will succeed will be the one that has its "foot in the door" in military units and has support of the most large manufacturers. Whichever can gain some Mil/LE success with the support of the most industry will become most popular because of the economics of scale (and thus reduced cost).

This is just like how commercial success happens in many other areas. BetaMax was superior to VHS but failed because of licensing and marketing. In the computer architecture field, people are still bemoaning Alpha's death to other less elegant architectures.

I bought a 6.8SPC upper as soon as I could. Why didn't I buy a 6.5Grendel upper? Even if you ignore the magazine issue (not resolved on the 6.5 side, I think), the reason is simple: economics.

6.8SPC sprung from military (albiet, S.F.) demand. It's already in the field. There is allegedly demand for more of them - as many as they can get. Military and LEO adoption virtually assures the "volume" numbers necessary to reach a critical mass where the economics of scale kick in. Prices will drop and more manufacturers, big and small, will want to get in on the action. This is how .40SW came to be, and now it is almost as cheap to shoot as 9x19.

There are a gazillion boutique and specialty cartridges you can chamber an AR15 for: .222, .223AI, 6mm-223, .30Whisper, 6PPC, .458SOCOM, .50Beowolf, etc, etc. Those are just the ones I can name off the top of my head. .223AI offers a good 200-300fps over .223. Why don't numbers of people shoot it? Because the cost and hassle to shoot it is too much.

IF 6.8SPC adoption continues, even if the regular army doesn't get it, the price of ammunition will be much more affordable than any other AR wildcat which does not have the mil/LEO demand. And replacement parts will be more common.

-z

 

[TX65]

If the basis of the 6.8 performance is ability to provide fragmentation, I think it would be fair to say that until independant terminal ballistics tests are run, any declaration of superiority in this area would be premature by either cartridge. However, I will put forward that a bullet of high ballistic coefficient has an inherent advantage in it's ability to extend the range of fragmentation since fragmentation is an attribute occuring within a defined velocity envelope. Given that the .277 115 OTM is of similar design to 6.5mm 100, 108 and 123 projecitiles, the same performance capabilities are there.

As far as military interest in the 6.5 Grendel, while I will not disclose the military orders received or commands making such orders as a matter of policy ( Barrett has a similar policy). I can say that clear military interest exists and I will leave it at that.

I think comments relating to magazine performance of the 6.5 Grendel are completely unfounded given that none of the people expressing a view have been involved in the testing and development of the cartridge or rifle, let alone having fired one. On May 7-8, military personnel will be given the opportunity to fire the production 6.5 Grendel with magazines at the Armed Forces Journal event at Blackwater. In addition, customers who have purchased 6.5 Grendels will be receiving their rifles, uppers, magazines, brass, ammo and reloading dies in the near future.

From a perspective of economics, 6.5 Grendel rifles and uppers in 18.5" and 24" barrel lengths are available with uppers priced at $875.00.

As far as major manufacturer involvement in the 6.5 Grendel... one may want to look at http://www.nammo.com --- the producer of the brass whose involvement in the defense industries is pretty evident making small arms ammunition, propellents, missles, artillary rounds,, etc. In addition, two well known bolt action rifle manufacturers have expressed their interest in producing 6.5 Grendel rifles.

Regarding the 50 Beowulf,,,, I guess the fact that thousands of Beowulf rifles / uppers have been sold and over 1,000,000 rounds of ammunition and brass produced makes it a boutique cartridge.

 

[only1asterisk]

Zak, John, Mr. Brennan, et al

I apologize, I'm having serious computer problems and have lost a couple of post along with some work. There are 3 computers on my desk right now and this is the only one with internet capablity at this point of the night. It refuses to cut and paste, so no spell check. Please forgive any errors.

Also please forgive my skepticism. With the lack of available information and the generally poor quality of what is available I am just stating my concerns. I believe people's chrono results with the 6.8 SPC, I just question the loading process, powders, pressures and if this ammo is going to stay this fast. Likewise, I believe Mr. Brennan when he says the 6.5 Grendel feeds. My question is can it do it day in, day out in all conceivable conditions. There is no doubt that it can be made to feed pefectly, but what will you have to compromise?

It is clear that there is an issus I hadn't really considered. Many people what this round to serve several purposes in the same rifle. I'd never consider hunting with an AR. I have hunting rifles for that purpose. There is nothing wrong with it, I simply have other tools. The same holds true with punching paper. Some people want a SUV, when I want a 4x4 that will never see pavement. For those that want a do it all rifle, the 6.5 Grendel may well be your round. It offers great factory hunting loads for game up to big deer. Enjoy. I'll hunt with a 6.5 Grendel too, only mine will be a bolt gun.

I see the AR familiy (to include all military versions and hereafter only refered to as AR) a fighting gun. It may be limiting, but thats how I see it. The AR only has one flaw in my book. I hate the fact that it was built to scale for the 5.56. This makes it hell to upgrade to a cartridge like those that we are discussing. You have to deal with the OAL. You either choose a short round with a more effecient bullet or a longer round with a less effecient bullet. You can't really have both because the result ends up being about 2.40"
long. I'll call this the AR compromise. The 6.5 Grendel address the issue with it's short and fatter case and long, lean bullets. The 6.8 SPC goes the other way with longer, narrower case suitable for use only with bullets with a less efficent shape.

In theory, the 6.8 SPC should have an advantage in feeding because of the shape of the round. In practice, quien sabes? At a minimum it should take less adaptation. The 6.5 Grendel is going to have more retained velocity, there is no two ways about it. If the 6.8 SPC fails to live up to its early velocity numbers, then the advantage can only grow. The rounds should have nearly the same velocity with equal weight bullets at equal pressures (within 1 or 2 percent I'd guess). The larger bore of the 6.8 SPC is offset by the 6.5 Grendel's slightly greater powder capacity. So what gives? I think it has to be some combination of greater pressure, supercompression of powder, a new powder type, slow twist barrel, two diameter bullet or a low friction rifling configuration. I don't have anyother way to explain the results. I'm REALLY curious about this! I am dying to get my hands on some production ammo and fired cases.

Again, my perspective on this is slanted in favor of combat.

I think the combat effectiveness of the AR would be greatly enhanced with the switch to ANY intermediate round. If I had my way, it would be tested in the Middle East right now and adopted across the board after it had proved it's worth. I think the switch to a larger service round need to be given priority, esp over a new weapon in 5.56. The thing I like best about the 6.8 SPC is new weapons can be designed to take full advantage of it's case length. While the 6.5 Grendal has some advantages now because of the AR compromise, the new rifles and squad automatics could be designed around the 6.8 round with a more longer, more efficient bullet and 2.40" OAL.

Pity that isn't the way the military works because I want one!

The intermediate cartridge COULD replace the 7.62 in significant portions of the GPMG and sniper roles, but why? We a do pretty good job keeping our troops supplied with the 6 or seven different calibers of small arms ammo they use now in all it's variants. What I think they need is a better standard infantry cartridge.

The 6.8 case lacks a esp. sharp shoulder, excess body taper (bad in the AR, not so in other weapons), a rebated rim or any other feature that might detract from it's feed reliability both in the current AR and future small arms. It's body diameter is closer to bullet diameter, which is a good thing for feeding as long as you retain enough shoulder for headspacing. Thesmaller rim diameter leave more of the bolt intact. All considered, I think it as close to ideal as you are likely to get (in a weapon for combat). Any improvement would be meaningless in the current rifle.

I need more infomation. I need data, raw data. Pressure numbers like SAAMI max average and max probable lot mean. Any physical measurements, chamber, reamer or case drawings, fired cases or loaded rounds. I want to see these things, not a article saying it can kill a deer in a gun mag.

It is either great marketing or really bad maketing. I'm ready to buy, but everyone wants to keep secrets.



David

 

[Grendelizer]

Zak, to answer your question about mag capacity. In a magazine with the external dimensions of a 30-round 5.56 mag, and if you increase the interior volume by easing out the ribs on one side, that mag will hold 25 rounds of 6.5 G and 28 of 6.8. In practice, manufacturers of both are making new magazines from the ground up for optimum performance.

My basic point about bullets with the 6.8 and 6.5 is that there are no magic bullets. However, in bullets of similar design, I contend the 6.5 performs better. Is your bullet designed to fragment? The 6.5 gives you a greater mass of fragments. Is your bullet designed to hold together and penetrate? The 6.5 gives you deeper penetration because of its sectional density.

A question for you and MLC, who said, "The 6.8 was designed from the ground up to be a CQB to intermediate range cartridge. The 6.8 is not meant to be the premier CQB to long range sniping do it all in one shot round of the 21st Century." I hear this all the time and would like to know what is really meant.

How do you design a cartridge to be CQB to intermediate range? Do you purposely limit the powder capacity? The Grendel has only a few grains more capacity, and yet it fits in the SAME action length. Do you choose a bullet that fragments? As I've mentioned, any cartridge can be loaded with fragmenting bullets.

How is a cartridge that is "designed" to perform from CQB to Intermediate different from one that DOES ALL THAT AND the long-range work besides, as the "do it all in one shot round of the 21st Century"?

Does the 6.8 have some special military "magic" that the 6.5 lacks? If so, what exactly makes it a "military" round versus the 6.5 Grendel? Have you seen pictures of the post-WW2-era .280 British? The cartridge proportions, the length and shape of the case relative to the length and shape of the bullet, mirror the look of the 6.5 Grendel. Refer here: http://www.65grendel.com/arcartridgephotos.htm and look in the third group of photos from the top.

The .280 British was designed specifically as a military cartridge; how is the 6.5 Grendel any less? It can't be the shape. It can't be the bullets. It can't be the powder capacity. It can't be the action it works in. Are you truly arguing the 6.5 is somehow less of a military cartridge than the 6.8?

John

P.S. I jump out of bed and run downstairs to the computer because it occurs to me that the .223/5.56 and .308/7.62 both started life as commercial, civilian cartridges. Does their civilian lineage make them any less military cartridges than the .30-06?

 

[Zak Smith]

I think comments relating to magazine performance of the 6.5 Grendel are completely unfounded given that none of the people expressing a view have been involved in the testing and development of the cartridge or rifle, let alone having fired one. On May 7-8, military personnel will be given the opportunity to fire the production 6.5 Grendel with magazines at the Armed Forces Journal event at Blackwater. In addition, customers who have purchased 6.5 Grendels will be receiving their rifles, uppers, magazines, brass, ammo and reloading dies in the near future.

Well, what is the deal with 6.5 mags? At this point, we know what the 6.8 mag situation is, but we don't know what the 6.5 mag situation is. If you want to dispell this uncertainly, tell us!

It's certainly not in the FAQ Gredelizer posted.

From a perspective of economics, 6.5 Grendel rifles and uppers in 18.5" and 24" barrel lengths are available with uppers priced at $875.00.

And Model 1 sales is advertising 6.8 uppers for about $400. This isn't relevant. The ammunition cost is most relevant.

Regarding the 50 Beowulf,,,, I guess the fact that thousands of Beowulf rifles / uppers have been sold and over 1,000,000 rounds of ammunition and brass produced makes it a boutique cartridge.

No, the end-user per-round cost and scarcity make it so.

-z

 

[Zak Smith]

David,

I've got fired cases, loaded ammo, and a caliper, but no pressure barrel.

Are there any measurements I can provide that would help?

With regard to hunting- If the 120gr Barnes X's work well in 6.8, my 18" with a Magpul stock will make a nice lightweight deer gun that either I or my SO of smaller stature can use. It will be just as at home shooting 3Gun, or standing "nightstand" duty.

-z

 

[Zak Smith]

Also note that the sectional density of the 115gr 6.8's is greater than the sectional density of M193 or M855, and only about 5% less than the S.D. of 150gr 7.62NATO.

re: mags. So, are legal mag conversion kits available for 6.5, so someone could convert a common pre-ban 30-round AR15 mag to use 6.5? (Ie, are the resulting mags interoperable-enough with the original mag/platform, as far as the BATF is concerned?)

How do you design a cartridge to be CQB to intermediate range? Do you purposely limit the powder capacity? The Grendel has only a few grains more capacity, and yet it fits in the SAME action length. Do you choose a bullet that fragments? As I've mentioned, any cartridge can be loaded with fragmenting bullets.

If I wanted an optimum cartridge for CQB against opponents with no body armor, I would probably choose something like 10mm or .45ACP. Those are flying ashtrays compared to any rifle round, with 25% less S.D. than 115gr 6.8. Likewise, if recoil weren't a problem, .458SOCOM, .50Beowulf, or even 00 Buck or slugs would make a great CQB round (overpenetration excepted!). However, it's obvious that those aren't suitable for shooting out to 300 yards: their trajectories are rock-like at those ranges. I think this is the compromise 6.8 intends to split.

From another point of view, what makes the 6.8 more "military" at this point is that they're actually using it in the field already (ref. economic and ubiquity argument).

-z

 

[Zak Smith]

Is your bullet designed to fragment? The 6.5 gives you a greater mass of fragments

Since you are obsessed with ballistics: No, it does not give a greater mass given the same muzzle velocity. According to the PDF, you are comparing the 115gr 6.8 @ 2700 with the 123gr 6.5 @ 2600. The comparable 6.5 is the 108gr @ 2700. And note that this is still using the errant 2700fps MV for 6.8SPC from a 20" bbl.

As expected, the larger diameter round can develop more velocity with the same mass bullet than a smaller caliber- the pressure has more area to work on.

-z

 

[only1asterisk]

Mr. Brennan,

Lapua brass is indeed a fine reason to choose a 6.5 Grendel over the 6.8 SPC. Their quality is great and a factor in my decision to build a rifle in this caliber. As for speculation about the feed reliability of the 6.5 Grendel, I wasn't invited to work on the project. While I feel those responsible for the 6.5 Grendel have been more forthcoming that others, the lack of details on the magazines leaves the subject ripe of speculation, Esp. since no AR chambered for a 7.62x39 derived round has been acclaimed for great reliability (Quite the opposide, in fact!).




John,

The was a cartridge produced 1958-60 during the T&E of the Armalite rifles( and various cartridges) for them that is very similar to the 6.8 SPC necked down to 6.35mm. The fact that certain ideas tend to resurface from time to time and are arrived at independantly by people with little or no knowledge of each other doesn't mean that they are the answer, but it may require investigation.

Zak,

I'm not against hunting with AR's, I'm going to build a couple of bolt guns with my own reamer specs when the time comes.

How do these numbers sound?

Rim diameter: .421"
Shoulder Diameter:.402"
Neck Diameter: .298"

Length to shoulder: 1.300
Length to shouder-neck junction: 1.425
Case length: 1.675

David

 

[Tony Williams]

A very interesting and well-informed debate, gentlemen.

Just a couple of comments:

Fragmentation and penetration are not mutually exclusive. Fragmentation occurs while a bullet is tumbling due to the stresses imposed as it passes side-on through a dense medium like flesh. But bullets don't tumble until they have entered flesh, or have hit something which has disturbed their flight. So a bullet which will fragment can still penetrate through body armour or cover first.

Possibly the ideal military bullet design would be divided into two halves (separated by a cannelure to encourage fragmentation). The back half would be lead. The front half would have a long steel core (for penetration) surrounded by light alloy (to keep the weight well to the rear, which encourages fast tumbling).

I'm not quite sure where we are with the Hague Convention on such bullets, however. Up to now, the fact that bullets tumble has been an after-effect of the spitzer form which shifts weight to the rear, making them inherently unstable (early round-nose bullets didn't tumble, they drilled neat holes, which is why the old 6.5mm Carcano military rounds acquired a reputation as ineffective). Fragmentation was something of a surprise when it occurred with the rearly 5.56mm bullets, and still does not form a part of the military specification; it was just an accident. But the type of bullets we are discussing here are very obviously being designed to fragment, which means they could well fall foul of the Hague injunctions against bullets "designed to cause unnecessary suffering" (or some such). No doubt the JAG is keeping an eye on this.

I did ask a question earlier about the latest position with regard to the military status of a new round. It's been said that the 6.8mm is being tested in combat. In what sort of numbers? To what extent is its use spreading? And does anyone know whether the Army (as opposed to SOCOM) is seriously interested in the possibility of adopting a new intermediate round with the XM8?

Tony Williams: Military gun and ammunition website and discussion
forum

 

[only1asterisk]

Tony,

I have serious doubt that the US military will adopt any new round anytime soon. It makes to much sense. There is also the weight factor to consider and a million studies to do. I'm not going to hold my breath.

Edit to add: Screw the the Hague, pass the expanding ammunition!


David

 

[TX65]

6.5 Grendel magazines -

The 6.5 Grendel magazines are done and will ship at the same time as the uppers and rifles.

As far as capacity,,, the standard 10 round magazine is longer then a .223 10 round magazines and shorter then a .223 20 round magazine. In the same length of a .223 20 round magazine, there is an 18 round magazine. In the same length of a .223 30 round magazine, there is a 25 round magazine. Increasing the length of the magazine slightly, as PRI has done with the 28 round 6.8 magazines, 28 round capacity is achieved with the 6.5 Grendel.

As Zak has stated, the issue with feeding larger diameter rounds is the internal width of the magazines, standard .223 magazines have vertical spacer ribs for the 5.56 / .223 cartridge. The 6.8 SPC and 6.5 Grendel require a change in these spacer ribs to accomodate their larger beltline.

As far as offering a conversion program as Armalite does (kit is an improper description since you have to send your M14 magazines in for conversion to insure compliance with BATF), that has been discussed and the decision of whether to offer a conversion program will be based on the AWB situtation coming into focus. In reality, it is more economical to just sell a complete new manufacture magazine then it is provide a conversion program in the manner approved by BATF, but again a conversion program is under review should the legal environment not permit sale of new manufacture larger capacity magazines.

I appreciate you bringing forward what is the reason for your concern ( ie - past 7.62x39 magazine performance). If you look at the AK47 and the magazines, you will see the magazine has a continual curve and this curve is based on the stacking of the tapered 7.62x39 case. When you try to put the 7.62x39 in an AR15, it is impossible to have this continual magazine curve because of the magazine well which requires a straight section of the magazine. This straight section of all AR15 magazines is the reason the 7.62x39 have had feeding problems --- the 7.62x39 does not like to be stacked in a straight magazine.

In contrast, the 6.5 Grendel likes straight contour magazines since it does not have the case taper of the 7.62x39.

A comment about velocities,,, the velocities shown in the ballistics chart are what are reported by ammunition manfacturers,,,not what handloaders (experienced or otherwise) claim they can obtain. As far as pressures, the 6.5 Grendel velocities are obtained in a production chamber and barrel keeping pressures in the 46,000-49,000 PSI range.

 

[Grendelizer]

I made the point that the 6.5 Grendel in its basic 123-grain loading, if it used the same bullet construction as the 115-grain 6.8, would be more effective at fragmenting because it has a greater mass of material with which to fragment.

Zak replies: "Since you are obsessed with ballistics: No, it does not give a greater mass given the same muzzle velocity."

Hmmm. Perhaps we are talking past each other a bit because we haven't agreed on a definition of terms. When I speak of mass, I'm speaking --- for all practical purposes --- of the weight of the material. A bullet weighing 115 grains has a mass of 115 grains.

For example, a hand grenade weighing two pounds has a mass of two pounds. When that grenade blows up, it's blasting that two pounds of material all over. A 2-lb grenade has more mass than a 1-lb grenade. When a 2-lb grenade blows up, that two pounds of material becomes two pounds of fragments.

Likewise, a 123-gr bullet has more total mass, or weight, of material than a 115-gr bullet. And when a 123-gr bullet "blows up," the solid mass of material becomes 123 grains of fragments versus 115 grains of fragments.

That's one reason why I say the 6.5 Grendel is better in the category of fragmentation.

John

 

[only1asterisk]

Mr. Brennan,

Points all taken regarding 7.62x39 magazines. I only mentioned them because you refered to them above. The PPC rounds have been chambered in the AR at times, and they have very minimal case taper. They never achieved much success either, I assume because not enough effort was put into the magazines.
My reason remains that the case body of the 6.5 Grendel is very short in relation to it's diameter and OAL. These short, fat, bottlenecked rounds are very efficient and win benchrest competitions, they just have never fed very well, even in bolt actions built for them. Consider WSM line, the 6mm an 7mm Remington Benchrest rounds and the PPC's. None feed as smoothly as 8x57, 30-06 or 6.5x55. Conventional case are shaped the way they are for a reason. The farther you depart from this shape, the harder a reliable feeding is to achieve. I would consider it a great feat of engineering if the 6.5 Grendel feeds as well as the 5.56. I hope it works out, but you will have to understand that some people are going to have their doubts when you go against what has been proven to them by failure.



David

 

[Tony Williams]

That's one reason why I say the 6.5 Grendel is better in the category of fragmentation.

Grendelizer, please see my previous post on the subject of fragmentation. It depends on the details of the bullet design and construction, next to which its weight and shape are unimportant. The difference in weight between the two bullets is insignificant for this purpose, anyway.

Tony Williams: Military gun and ammunition website and discussion
forum

 

[MLC]

Grendelizers post

My intention in stating that the 6.8 SPC was designed to be a CQB to intemediate range cartridge was based on these ideas:
Our military, specifically SF units, is/are having issues with the lethality of issued 5.56 amunition.
The 6.8 was designed to fit in the existing M4/M-16 platform and enhance lethality by using a larger diameter bullet with better terminal performance.
The 6.8 uses a match type(boat tail, drawn copper jacketed hollowpoint) bullet as the Grendel does, but the 6.8's 115g OTM is shorter and less aerodynamic because it was designed with the intention of being used at shorter ranges, at human targets and fit in the magazine of an m4/M16/AR.
The 108g(closest comparible weight) Scenar was not designed to be shot at humans, it was designed to be shot at paper targets at long range out of a bolt action rifle.
I have already conceded that the 6.5 is ballistically superior to the 6.8 and also stated that I have a decided preference towards the 6.5.
I'm not trying to derail your marketing hype Grendelizer,
I'm simply stating that the 6.8 at this point is more of a military cartridge because the miltary is using it.
Perhaps if you were to post some documentation of ballistic performance of the Grendel other than target applications.
There is quite a bit of real world data posted on the 6.8.
As far as the 7.62x51 and the 5.56x45 starting as civilian cartridges
I disagree on both counts.
This the the stuff we see re: the SPC:

 

[TX65]

Hi David,

I can appreciate what has been past experience with the PPC, but maybe this can provide further detail.

1. Previous individual efforts with the PPC have been based on the 22 PPC and 6 PPC. Contrary to some reports, many people have achieved success in making both rounds feed which is an accomplishment given other factors that they may not have realized they were up against.

2. Speaking with many of the people who have built these rifles, all these attempts have used standard .223 barrel extensions. As has been made clear, the barrel extension is one of the key components to the system. Use of a barrel extension with the wrong ramp angles can complicate feeding with any cartridge.

3. The relationship of case body diameter to neck and bullet diameter is a critical element in feeding. Looking at bullet diameter alone, the 6.5 Grendel has .021" less difference in this relationship then the 6 PPC and .040" less then the 22 PPC.

4. The 6.5 Grendel is not a perfect straight body as some may visualize, the body diameter just ahead of the extractor groove is .440", the diameter of the body at the junction with the shoulder is .423" so there is taper in the body.

The barrel extensions and magazines were engineered to work with the 6.5 Grendel and they work and work well. I have had calls from people who have 22 and 6mm PPC AR's wanting to order magazines thinking "wow,,,no more individual tuning of magazines", but I make it very clear that no guarantee of function with the 22 or 6 PPC can be made because the barrel extensions and magazines were designed to work in unison and if you still have a .223 barrel extension, you are missing half the system. As well, because the geometry is designed around a 6.5m bullet and neck, using a 22 or 6mm increases changes in the geometry of function.

As a note to someone commenting about the 6.5 Grendel being developed by enthusists and target shooters. I guess I am the target shooter in the equation, but there are no enthusists. Bill Alexander is an engineer who has many years of experience in the British defense industries including working with elite British military units prior to coming to the USA and starting Alexander Arms three years ago. In addition, Dr Lou Palmisano (an accomplished surgeon, developer of the PPC cartridges and holder of 15 firearms patents) has provided valuable insight. As well, Lapua and Lothar Walther engineers have provided input.

 

[Zak Smith]

As far as offering a conversion program as Armalite does (kit is an improper description since you have to send your M14 magazines in for conversion to insure compliance with BATF)

False. They send you a mag body, follower assembly, and instructions how to disassemble your old M1A mag, modify the spring, and assemble the new one.

Hmmm. Perhaps we are talking past each other a bit because we haven't agreed on a definition of terms. When I speak of mass, I'm speaking --- for all practical purposes --- of the weight of the material. A bullet weighing 115 grains has a mass of 115 grains.

I understand the 123gr bullet has more material than the 115gr to sling around. My issue was that, at least according to the PDF chart, the MV of the 123gr is 100fps less than the 115gr bullet. It's not quite an apples-to-apples comparison. If you want the MV "bar" set at 2600fps, I'll let you know in a month how heavy of a bullet I can get up to 2600fps in 6.8

1*-

My reason remains that the case body of the 6.5 Grendel is very short in relation to it's diameter and OAL.

The 5.45x39 round is also pretty long in comparison to the case length. How does it compare dimensionally to the 6.5? 5.45 can obviously be made to work in rifles, though I don't think anyone's tried it in an AR15.

MLC, thanks for linking in that terminal ballistic information. Most of these are one "shot fired" at one terminal velocity. This is a good start but doesn't give us any statistical certainty, or a slew over a range of terminal velocities.

For example, when comparing the "effective range" of a particular load, we need to draw a line saying "above this terminal velocity, it's effective, but below this terminal velocity, it loses effectiveness" by looking at a series of experiments which changed velocity. Then we can calculate the effective range using the MV and BC.

-z

 

[TX65]

Zak,

As of current writing, you are correct that Armalite is once again selling the kits,,, there was a period of time were they were requiring that the M14 magazine be sent in as proof that someone actually had a pre-ban M14 magazine and did not purchase surplus floorplates from another source never owning a complete magazine. Of course, with them reverting to the old policy, the burden again falls back on the consumer to be able to proove ownership of the pre-ban magazine.

Again, a conversion kit or program (whether kit or program will be determined with approval by BATF) has been discussed and will be considered when the AWB situation is solidified either way. If the AWB ban sunsets and is not replaced by another nasty, a complete magazine can be offered and a conversion kit would be unneccassary.

Alexander Arms offers a 5.45x39 AR15 upper and rifle which they call the 21 Genghis. The chamber on this upper and rifle is designed specifically to allow use of steel case ammo such as that produced by Wolf. It is a great option for those seeking to use low cost ammo in high volume.

 

[Grendelizer]

Tony Williams wrote: "Grendelizer, please see my previous post on the subject of fragmentation. It depends on the details of the bullet design and construction, next to which its weight and shape are unimportant. The difference in weight between the two bullets is insignificant for this purpose, anyway."

Tony, I agree with you 100% about fragmentation. I'm not saying the weight CAUSES fragmentation, only that more weight gives more fragments.

I also agree the difference is practically insignificant. When we're dealing with cartridges, a lot of things are practically insignificant, if a person steps back and looks at the broader picture. When we're dealing with small differences such as one-third of a millimeter in caliber, we're dealing with one cartridge having only a slight edge over the other. But, these "edges" add up into true advantages at some point, don't they? Or why not just stay with 5.56 and say there's no room for improvement because any slight differences don't matter in the "real world"?

Let me turn the question around and ask you: At what point do differences become significant? The difference between 5.56 and 7.62? The difference between 7.62 and 9mm? The difference between 77 grains and 90 grains? Or 77 and 123?

John