6.8 vs 7.62x39


July 27, 2007, 05:36 AM
Is the new 6.8 round the military is looking at a better cartridge than the 7.62x39? I heard that Ruger will be offering the Mini in 6.8, and they already offer the rifle in 7.62x39. So would it be a step up or just something between the 7.62x39 and 5.56?


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July 27, 2007, 07:27 AM
You know it all depends on what you think is "better". The 6.8 (same caliber bullet as the famous .270 but less powder in the cartridge) was to replace the 5.56. IIRC it shoot flatter and farther than the AK round but is not as large or as heavy. The 6.8 has better terminal performance than the 5.56 but short range I believe the AK round is better. So I guess it all depends...

July 27, 2007, 08:10 AM
I'd say the 6.8 was probably a better choice if you will shoot at any distance at all (over 100 yds), but the 7.62x39 has the advantage of much cheaper ammo floating around if you wanted to stockpile for the zombie wars ;P

July 27, 2007, 08:24 AM
I love my AK's, but the freakin arc that the 7.62x39 has in flight is ridiculous.

July 27, 2007, 08:54 AM
My understanding is that the 6.8 is not in consideration for anything but special purpose use. It appears to be a very efficient intermediate round, but I wouldn't look for the wholesale abandonment of the 5.56 anytime soon.


July 27, 2007, 09:11 AM
I don't think anyone should go into a 6.8 with the idea that it will be adopted by the military and cheap ammo will be abundant. However, the round is doing very well in the civilian market, and is a nice medium round with alot to recommend it in it's own right. I just purchased a 6.8 AR upper I plan to use as a foul weather deer gun myself. Haven't had a chance to shoot it/sight it in yet because of rain and a busy schedule--hope to get it out soon if it'd stop raining!

July 27, 2007, 11:03 AM
Ruger displayed the Mini in 6.8 at SHOT (January) or NRA (April) or maybe both. I have one on order, but haven't seen it yet.

Although the 6.8 was allegedly developed by Special Forces to solve lethality issues with the 5.56, don't hold your breath on ANY new cartridge development coming out of DOD any time in the near future. There has been some SpecOps use of the 77 grain Sierra in the 5.56, but I haven't seen anything in writing showing improved lethality there either.

July 27, 2007, 11:09 AM
the 6.8 smokes them for various reasons, but the 6.5 Grendel would be better.

July 27, 2007, 11:15 AM
The 6.8 will perform better on large game than 223, and will be legal is states that ban the 223 for hunting. The 6.8 launches a 115 gn bullet at around 2650 versus the 7.62x39 at around 2400. I've been shootiong the 6.8 for a while, and it is a decent intermediate cartridge. I'd like to see it in a few lightweight rifles, and the Ruger would help popularize it.

The 6.8 is exactly the opposite of the big ultramags. It's a light recoiling, short range cartridge that perfect in a light weight rifle on medium game at shorter ranges. It is superior to the 7.62x39. It beats any commercial 30-30 load at 100 years, while some 30-30 loads have marginally better energy at the muzzle.

July 27, 2007, 11:53 AM
the 6.8 smokes them for various reasons, but the 6.5 Grendel would be better.
my understanding is that the 6.5 has more range, but there were problems getting the rounds to feed in belt fed guns, which is a major negative for military use.

July 27, 2007, 12:10 PM

Domestic barrel in 6.8 SPC milled to same profile as Galil barrel

Galil mag adaptor for AR style magazines

bit of mill work...

Could be trouble... or the start of a 6.8 SPC Galil...

July 27, 2007, 12:13 PM
External ballistics on the 6.8mm are much better than 7.62x39, and you only give up less than ten grains in bullet weight with military loads (115 grain 6.8 versus 123 for the AK round). Downside on the 6.8 for hunters and such is that you can't run much heavier bullets due to the requirement to feed through the AR mag well (Grendel has the same problem to an extent) -- but the 115 grain weight should work for deer in any case.

July 27, 2007, 12:29 PM
The bullet weight issue is only a problem if it has to fit in AR mags.

I'd have to look at a Galil, but to convert to 6.8 you have to open the bolt face. 223 has a 0.383 bolt face, the 6.8 has a 0.422 bolt face and the AK around 0.45 It may or may not be possible to get the extractor to work, thanks to the way the AK derivatives mount their extractor.

A copuiple of years ago I converted a Kel-Tec SU-16 to 6.8. It was not trivial.


July 27, 2007, 12:36 PM
Is this going to turn into the rifle version of the 9 vs 45 debate?

Zak Smith
July 27, 2007, 12:51 PM
6.8 SPC was designed specifically (or, more accurately, it was the outcome of a project to design a cartridge-) to provide optimal terminal performance from an M4 with minimal changes to the platform. Specifically, the barrier penetration ability of 7.62x39 was desired.

Cartridge assessment began with the 6mm PPC case, necked up to 6.5mm. The 5th
SFG soon discarded the fat PPC case due to poor magazine capacity and
insufficient reliability in the M4. Their attention then turned to the .30
Remington case, which is essentially a rimless .30-30 Winchester. Its head and
body diameters are larger than 5.56 (0.378 inch), but smaller than 7.62x39mm
(0.445 inch). This thoroughly obsolete cartridge was chosen as the parent case
because its smaller head diameter (0.422 inch) required less metal to be cut
from the bolt head compared to the PPC or 7.62x39mm cases, which improves bolt
service life. Several rebated-rim prototypes were created with an SPC body but
5.56's rim (0.378 inch) to utilize unmodified M4 bolts. After trials, it was
clear the full-diameter rim helped extraction as compared to the rebated rim

Once the case dimensions were tweaked to fit and work in M4-compatible
magazines, the project team quickly turned their attention to bore size.
Derivative wildcats from 5.56mm to up 7.62mm diameter shooting bullets from 90
to 140 grains were subjected to a battery of tests, and a sweet spot emerged.
The 6.5mm bullets showed the best accuracy and the 7mm bullets were the most
destructive, but the 0.277-inch bullets showed almost the same accuracy and
trajectory as the 6.5mm and almost the terminal performance of the 7mm. When
necked down to 0.277-inch and shooting 115-grain bullets, it provided the best
combination of combat accuracy, reliability and terminal performance for up to
500 meter engagements. This cartridge was deemed 6.8 Remington Special Purpose
Cartridge (SPC), because 0.277 inch is 6.8mm in metric and .30 Remington
provided the parent case.

Numerous articles and Internet rumors have suggested that the SPC designation
means 6.8 is good only for Close Quarters Battle (CQB), but not distant targets.
This is incorrect, and contrary to the intent of the project and capabilities of
the cartridge. The SPC designation was assigned based on the intended
integration into the Mk12 Special Purpose Rifle (SPR). The SPC was designed
from the ground up to provide increased energy, barrier penetration, and
incapacitation from the Mk12 SPR, from contact distance to 500 meters.

Based on their experience with 7.62x39mm, the project team set a velocity goal
of 200fps faster than the AK-47 ammunition from the same barrel length, with a
projectile that provided a better ballistic coefficient (BC) and terminal
performance. This was achieved very soon into the project using Sierra
115-grain and Hornady 110-grain Open-Tip Match (OTM) bullets. Using Ramshot
1660 powder for initial development, the team easily exceeded the 200fps goal.
Shooting from an 18-inch SPR barrel, these loads shot 2635 to 2650fps, 300fps
faster than the AK-47.

July 27, 2007, 08:27 PM
Hey Folks – Thanks for all the input.

Here is what started me thinking about this. I have an older Mini-14 that has been super reliable for me and, believe it or not, shoots nice groups at 100 yards, which is just about the maximum urban range I figure I would have to ever use it at. The only drawback for me is that the 5.56 is weak when it comes to barrier penetration. I have seen treated 2x4s sometimes turn the bullet into basically rat shot down range. I had considered replacing it with a Mini-30, especially now that a few changes have been made to improve accuracy and come up with a nice set of iron sights. Then, being the gun enthusiast that I am, I heard it would be available in the 6.8 and thought hummmm, ya know what, may I should ......

This carbine would end up being a truck or vehicle defensive tool and would be sighted in at about 50 yards with a maximum expected range of 100-150 meters. I prefer the Mini over the AR variety because of the small distance between sight line and barrel axis. At 10 yards, I can hold dead on, where with the AR I have to hold a little high. I also don’t have to be as cognizant of the muzzle clearing cover along with the sights. The Mini also does not have as much of an “evil gun” appearance as the AR or an AK does. A plus in case some tree hugger accidentally catches sight of it.

It would seem that the 6.8 would give more punch and less drop at 300+ yards than the 7.62x39, but this is not where I expect to use it. I guess the availability of less expensive practice ammo leans me towards the 7.62x39. I figure if I went with 6.8, that at least for a while I would have to reload or buy expensive ammo. I think Corbon could come up with a 115-grain solid copper DPX for the 7.62x39 and get it to do almost as well as the 6.8

Thanks Again - TEX

July 27, 2007, 11:45 PM
samx, you are right on the grendel, the neck / shoulder is short, and it goes right up the end of a feed pawl, on a 249 saw, which means, either the round case has to change a bit, or they have to modify, the feedpawls of the 249 a bit, which is a big no go, do not pass this station. that being said, it's performance actually surpasses the 308, after about 500 or 600 yds.

July 28, 2007, 12:57 AM
The big problem I see is that everyone is tryiong to make a better cartridge and stuff it into a platform that was built around the 5.56x45mm. For a combat cartridge, 6.5 Grendel has the feeding problem, plus a case that doesn't have enough taper for a truly reliable auto weapon. One of the big advantages of the M43 7.62x39mm is that it's extreme body taper makes for superb feeding and even better primary extraction. Such an extreme taper may not be necessary for high reliability, but the essentially non-existant taper of the Grendel is a liability in a weapon that may be exposed to extreme conditions.

The 6.8 may be a little better, but it is still a baling wire solution. If we are really looking for a better cartridge, we need to start with the round, and build the gun around it, not the other way around.

I picked 6.8 over 6.5 Grendel because Remington was backing the 6.8, and Alexander Arms was being very propriatary with their round. At one time, you could not buy 6.5 reamers, but had to get barrels from an AA approved maker. Right now, I can walk into my local gun store and buy 6.8 ammo. They keep saying 6.5 is coming from Wolfe, but I have yet to see it.

If either round is ever going to be something other than a niche cartridge, they need to be loaded into suitable rifles. Remington's 700 variant ain't it. Why buy a rfile in a puny cartridge, when the same rifle can be had in something far more effective. I'd like to see the 6.5 or 6.8 in something like a CZ-527 - a small, light rifle sized for the small cartridge.

Then again, you'd still be fighting the supermagnum trend. I have people contantly tell me that the .260 and the 7x57 are under powered for hunting. Where does that leave a cartridge like the 6.5 Grendel or 6.8 SPC?

July 28, 2007, 03:05 AM
The big problem I see is that everyone is tryiong to make a better cartridge and stuff it into a platform that was built around the 5.56x45mm.BINGO.

If this, or any other cartridge, is just going to be a supplement to 5.56 NATO, this makes sense. However, if they're looking to move beyond the M16/5.56 family of weapons, it makes no sense to do what they're doing. They are, simultaneously:

A. Designing a new round, intended to fit in the M16/M4 magwell. Sources vary on how much effort is being put into this by the military, with most of the credible ones saying "none at all". Others will know more than me, however.

B. Desiging a new rifle, to shoot 5.56 NATO (SCAR).

Now, if I were serious about making a step forward in small-arms development, I would remove the constraints of the one from the other. Design a new round and a new gun to shoot it. The fact that they're not doing this tells me that the military is not ready to make any major step just yet.


Zak Smith
July 28, 2007, 02:26 PM
The SCAR was intended to shoot multiple calibers.

July 28, 2007, 02:52 PM
The SCAR was intended to shoot multiple calibers.
They are being produced in three calibers.


July 28, 2007, 02:57 PM
What is the actual metric of the 6.8s bullet? I'm reading here it is .277 but the Ruger website says .270. Obviously the confusion is that the .270 Win bullet is .277.

July 28, 2007, 02:58 PM
Years ago i was looking at the hot new item 10mm vs standardizing on 9x19.
I went with 9mm luger because it was more available and has been around a while. It is much easier to keep my 9mm's feed now than 10mm.

July 28, 2007, 03:07 PM
What is the actual metric of the 6.8s bullet?
In metric, it's 6.8mm. :neener:

July 28, 2007, 04:12 PM
"Metric" means a measurement whether it is expressed in inches or the "metric" system. Again, the question is: .270 or .277? Maybe no-one knows? I think it is .277 since that is closer to a true 6.8mm, but it is being called .270 all over the place.

July 28, 2007, 04:20 PM
"Metric" means a measurement whether it is expressed in inches or the "metric" system. Again, the question is: .270 or .277? Maybe no-one knows? I think it is .277 since that is closer to a true 6.8mm, but it is being called .270 all over the place.
Just messing with you. :p

I concur with your assessment that it's .277.

.270 is just what the manufacturers calls it. Probably for marketing reasons. Kinda like why .38 Special & .357 Magnum are really .355 and .50AE is really .495.

July 28, 2007, 04:45 PM
SSK also developed a round to suplement the 5.56 that was given a trial along with the 6.8SPC, it was the 6.5MPC. The MPC had a 107gr bullet that would achieve 2400fps out of a 12" barell, and around 2600 out of an 18", it had the same OAL, rim and width of the 5.56, but was basically necked up a little, and some minor tweaks to fit more powder in the case, but basically the only thing that needed to be changed on M-16 or M-249 platforms were the barells, even the standard 5.56 mags and links worked, too bad that one didn't get the green light, brass, bullets and a barell or upper would be all I need. 6.8 seems neat, but unless cheap surplus is expected (Im not holding my breath) I am going to stay wih my AK and AR rifles. For my purposes there is not much 6.8 will do that either of these can't.

July 28, 2007, 06:26 PM
6.8SPC uses bullets that are 0.277. Due to magazine length, you are limited to bullets under about 115 grains.

July 28, 2007, 06:39 PM
They are being produced in three calibers.


A 6.8mm Rem SPC version of the SCAR-L was in the cards until SOCOM's trials of the round indicated they'd prefer to stick with 5.56mm. The change would still be about as easy as changing caliber on a LMT MRP upper -- barrel and bolt and mags and you're in business.

July 28, 2007, 07:56 PM
6.8 supposedly gives you most of the 7.62x39's knockdown power at close range while shooting even farther and flatter than the 5.56 NATO. One thing to consider is price, though - good luck if you can find 20-round boxes of 6.8SPC for under $18-20...

July 28, 2007, 08:38 PM
The SCAR's development in multiple calibers is, as I understand it, based upon two frames, the SCAR-L and SCAR-H. The "light" version uses a 5.56x45 M16 magazine compatable well and the heavy uses a 7.62x51 magwell of some sort (M14? Proprietary? I'm not sure).

Unless my statement about the SCAR-L being based upon 5.56 NATO dimensions is incorrect, I think the basic gist of my comment remains true. It's not like they allowed for the development of a 6.8-esq cartridge that is 46mm in OAL for the SCAR-L. It's still tied to the OAL if the 5.56 NATO cartridge.


Zak Smith
July 28, 2007, 11:12 PM
I thought 7.62x39 played in there somewhere, considering SPR-V. Online references say the SCAR-H was convertible to 7.62x39 (??).

The only other thing I have to add is that being designed around the M16 magwell vs. "designed around 5.56 NATO" need not be the same thing. The viable assault rifle cartridges are all more or less the same length, and I think most would agree the action and weapon size resulting from 5.56/7.62x39/etc-sized cartridges is compelling over longer cartridges. There's no need for the mag-well to be fixed in one of these modular weapons systems-- viz, the Masada.

July 28, 2007, 11:40 PM
Right, but what I'm saying is that the SCAR is designed that way. That, combined with the fact that 6.8SPC was mandated to fit within standard M16 magazine dimensions, is evidence that they're not seriously thinking about moving too far beyond what we have right now. If you were thinking about doing something different, you would design a new weapon and a new round without the limitations of either of the old components.

I agree it does not have to be that way. They are, however, doing it that way.


July 29, 2007, 12:20 AM
Agreed. What the 6.5/6.8 should have been.

Personally, I'll take 6.5 as there are better bullets, so long as we are not confined to M16 magazines.

The ideal round should be relatively light vs.the 308, moderate body taper for good feeding, have goot short range killing power, and good moderate range petformance. Ideally, it shouyld also be effective at long range for DMRs and GPMGs. It should also have relatively low recoil for full auto use.

For my bullet I pick the 6.5 123gn Lapua Scenar with a BC of 0.547. I want the recoil under full auto to be controllable, so it must not be much more than the AK. We set our velocity target from an 18inch bbl for 2600fps. With a rifle weigh of about 9 pounds stripped, this gives us more recoil than the M16, an a touch more than the AK. Assuming a muzzle brake, this is reasonable recoil, even under full auto. The 6.5 grendel can manage 2400 with this bullet, so we will require a longer case to gain velocity and enough taper to ensure reliability.

How does the round compare with the current issue 5.56x45 and 7.62x51?

Recoil: The 6.5 has about half the recoil of the 7.62x41, and about 1.8x that of the 5.56.


cartridge 0 100 200 300 400 500 600 700 800
M855 1239 1019 832 673 538 426 335 264 210
6.5 1846 1649 1469 1305 1155 1019 896 787 689
M80 2502 2145 1829 1551 1306 1094 912 758 631

the 6.5 proposed comes very close to 308 at moderate ranges, and overtakes it long range. This with a lighter bullet going slower

A second variation of the 6.5 using the 108gn Laupa scenar at 2800 fps yields slightly less recoil, about 1.5x that of the 223.

cartridge 0 100 200 300 400 500 600 700 800
M855 1239 1019 832 673 538 426 335 264 210
6.5 1880 1658 1458 1277 1114 968 838 722 621
M80 2502 2145 1829 1551 1306 1094 912 758 631

It seems that we can pretty easily create a cartridge that comes very close to 7.62x51 without the heavy weight or recoil of 308. Get the bullet to fragment like the M855 and M193, and it beats the 5.56 in every way.

July 29, 2007, 01:04 AM
The bullets called for in all the loads are the same as used in the .270 Win. I've used 110 gn, 115 gn, and even 130 gn bullets in my 6.8 loads out of my AR. I suppose the 130 grain loads come out pretty slow, but they will certainly be affective on game out to 200 yards. Shooting at 200 yards, I notice about 8-10 inches more drop than the 115 grain bullets, and the load data guesses that they come out around 2200 fps compared with 2600 fps for the 115 grain loads. I don't know for sure, since I don't have a tach.

July 29, 2007, 01:30 AM
You can get a pretty good estimate of velocity without a chronograph iof you measure drop and get the barometric pressure where you are shooting.

What rifle are you using? I thought about 130s, but didn't like a compressed charge to seat them deep enough in the mag. 110s and 115 seem like the best balance, but Zak is the 6.8 guru.

July 29, 2007, 01:42 AM
I'm using a home-built 6.8spc with a barrel from ko-tonics (http://www.ko-tonics.com). Has an "improved" chamber that can handle higher pressures. Pretty nice rifle.

July 29, 2007, 02:42 AM
OK, 6.8 in an AR-15.

Some are using 6.8 in a turn bolt, which give a little more room for longer bullets.

July 29, 2007, 10:38 AM
I thought 7.62x39 played in there somewhere, considering SPR-V. Online references say the SCAR-H was convertible to 7.62x39 (??).

I believe you are correct. From what I understand, the 7.62x39 versions or conversions are going to be a low basis of issue kind of niche weapon to replace the SR-47s.

July 31, 2007, 12:58 AM
Just a couple corrections:

GunTech wrote: "Such an extreme taper may not be necessary for high reliability, but the essentially non-existent taper of the Grendel is a liability in a weapon that may be exposed to extreme conditions."

Tod, the Grendel has more taper than 5.56, more taper than 6.8, more taper than 7.62 NATO. Only 7.62x39 has more.

GunTech wrote: "They keep saying 6.5 is coming from Wolf, but I have yet to see it."

It's here, and it's been here. I just shot 80 rounds of it yesterday! Alexander Arms, of course, sells it. Cabelas sells it. MidwayUSA sells it.


July 31, 2007, 01:48 AM
Grendelaizer, can you provide a cite?

According to my references (SAAMI and CIP), here's how the cases stack up. Note that 6.5 grenel is neither SAAMI or CIP.

Body taper

7.62x39 -- 1 degree 29 minutes 5 seconds
5.56x45 -- 30 minutes 5 seconds
6.8 SPC -- 29 minutes 3 seconds
6.5 Grendel -- 22 minutes 23 seconds.

Thus 6.5 grendel has the least body taper of the four catridges listed, not suprising since it is based on the 6mm PPC, a blown out 7.62x39 with a sharp shoulder.

6.8 and 5.56 have nearly identical body taper, and the 7.62x39 has aroun 3x the taper of the 5.56.

BTW, 6.5 Grendel is better than the 308, which has a body taper of 20 minutes 40 seconds.

July 31, 2007, 11:17 AM
Tod, it looks like you've done the math and I was just repeating something I'd heard.

Please tell me how to do the math, and I'll measure a case when I get home tonight.


July 31, 2007, 12:15 PM
wolf gold 6.5 grendel.

July 31, 2007, 12:19 PM
Is the Ruger mini in 6.8 on the market? Anyone here have one?

July 31, 2007, 02:21 PM
Please tell me how to do the math, and I'll measure a case when I get home tonight.

It's just trig.

Using .308 as an example:

Take the diameter at the head where the extraction groove bevel ends and at the shoulder - 0.470" and 0.454" respectively. Take the distance parallel to the bore between those two points - 1.435".

This gives you an isosceles trapezoid. Imagine trimming off the edges to leave the largest possible rectangle. The trimmings will be two right trangles with dimensions 0.008" perpendicular to the bore. and 1.435" parallel to the bore.

Let the side perpendicular to the bore be a and the side parallel to the bore be b

tan A = b/a. Which gives 0.314 degrees. Multiply that by 60 to get minutes - 18.84 minutes, or 18 minutes and (.84*60) 50 seconds.

This calculation does not exactly match the 0'20'40 spec, due to rounding errors or not measuring the same points on the case, but it's close enough for internet debate.

Back to the original topic of feeding, shoulder angle is at least as important as body taper.

6.5 Grendel - 30 degrees
.223 - 23 degrees
6.8 SPC - 23 degrees
.308 - 20 degrees
7.62x39 - 18 degrees

July 31, 2007, 04:06 PM
I cheat and derive the body taper in QuickLoad using either the SAAMI specs or CIP. Good point about shoulder angle too. IU meant to mentio it.

There's another thread about the ultimate combat round that this discussion dovetails nicely into. Think about what round you'd spec out if you weren't constrained by M16 magazine size.

Right now, I am thinking about something that

1. Has no more recoil than an AK in 7.52x39
2. Has superior energy at all ranges than the 223
3. Is suitable for a GPMG or DMR, with enough retained energy to be effective at 600+ meters
4. Weighs less than current full power cartridges
5. has pressure levels suitable for light weapons

I think the 6.5 is very close, but not quite there. I'm going to pick an arbitrary case head, and select the 30 remington/6.8 with it's 0.422 case head. I opt for a 1 degree body taper (halfway between 223 and AK) and a shoulder taper of 20 degrees. As a starting point, I pick the 6.5 using the Lapua Scenar 108 gn with a BC of 487. My target velocity is about 2800 fps in an 18 inch bbl.

More data to follow. I need to spec out my round in QuickDesign.

August 1, 2007, 01:06 AM
Not to stray too far off, but I could have sworn that tony rumore (tromix) did an AK conversion into 6.8? (and 458 as well?)

I'm pretty sure some of the AK homebuilders on gunco have done 6.8s.

August 1, 2007, 01:24 AM
Interesting. I would be touch to do the bolt face conversion on an AK, I would think. I suppose you could open up the bolt face on a 223.

I did a 6.8 conversion an a Keltec SU-16 and that was a major PITA. You can see the details on ktog.org

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