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I have 2 complete guns and a 3rd upper:
LWRC Six8 14.7" SPR Other
Custom build for hunting: 16" ARP/PRI rail
18" WOA barreled upper
All great shooters. They won't replace my 5.56 guns but supplement them only because of no source of reasonable cost ammo.
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Agreed, the cheapest I can find is Hornady AG 110gr BTHP and Prvi Partizan 115gr BTHP at around $0.58 a round. It would be nice if Wolf would makes some steel cased 6.8 SPC. They make steel cased 6.5 Grendel FMJ for $0.30. Although the bi-metal jackets do wear barrels faster (mild steel jacket that is copper plated / washed for lubricity) than all copper clad lead core bullets that are common in the US. Steel cases also don't seal as well (more blow by and carbon residue). I know from experience from my custom 5.45 upper. New production 5.45 wasn't as dirty as 7N6 though.Originally Posted by VLODPG
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Me either really. I designed the 6.8x39 now called the 277 Wolverine maybe 7-8 years ago. I asked all of the guys on 6.8 forums if I should produce them and not 1 person out of 38,000 said "yes it would be a cat they were interested in" so I did not make any barrels. About 3 years later Mark Kexel asked me about it and I gave him the design then made his first batch of 50 barrels. It does pretty good with lighter weight bullets and brass is cheap as dirt or free sometimes. I would use the 85gr TSX.
The problem I have as always is people comparing hot handloads of their favorite round to factory ammo and then saying yeah it's within 100 fps or it's almost as fast.
Now there is an "if" IF the 5th group had tried to get a 6.8 based on the 5.56 case adopted the mil may be using another caliber right now. It would have been much cheaper, same mags, same bolts and it would have been easy for Lake City to load.
Senior Member
The Wolverine offers "similar" ballistics to the 6.8 without any reduction in mag capacity and without any real change in recoil characteristics over .223.
It isn't a direct replacement for the 6.8 nor is it a replacement for the 300 BLK. But it does combine the good stuff of these two.
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“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter cannot be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles."
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KE is a poor predictor of penetration as it is not a vector quantity (does not have direction). One of the biggest issues bar none of the 5.56 is it's low momentum. Heavier projectiles carry more momentum (slug-feet per second) and thus retain retain KE better allowing them to pass through barriers with enough remaining KE to do some serious damage on the other side. We want to expend most of the KE in the target, not the barrier. So a more controlled expenditure of KE is needed than 5.56 projectiles can offer for optimal performance in real world applications (at least human vs. human applications or medium to large game applications).
I'll preface this with, there is NO perfect bullet. 6.8 isn't perfect and neither is 6.5 or any other. It's about balancing attributes to achieve the highest average of desired outcomes. Training practices such as failure to stop drills (two in the chest, one in the head) are designed to account for instances where one in the chest fails to achieve the desired results even though in a sizable percentage of instances it may (especially with bigger calibers having both greater KE, momentum and resistance to fluids).
A weaker 6.8 does have some advantages over it's 5.56 counterpart, but not by much because the loss in velocity over a 6.8 SPC or 6.5 Grendel reduces it's momentum comparably. You still need velocity.
Momentum for a 90gr projectile exiting the muzzle at 2500 fps = 4.58 @ muzzle (1,249 ft-lbs KE)
Momentum for a 75gr projectile (Sierra Match in a Hornady factor load) exiting the muzzle at 2739 fps = 4.17 @ muzzle (1,249 ft-lbs KE)
Momentum advantage for the .277 Wolverine example above shows a 9% advantage in momentum. Not huge, but at advantage none-the less while still having identical KE available. The disadvantage of the .277 Wolverine is going to be it's trajectory at longer ranges, it's going to have more drop due to it's slower velocity making it harder to use at longer ranges, which is also an important part of the equation.
Here's another example illustrating the real advantages of 6.8 / 6.5 over 5.56 taken from Horandy's best factory loads for 5.56 (, 6.8 SPC and 6.5 Grendel:
5.56 NATO momentum for a 75gr SM BTHP match load exiting a 16" barrel at 2810 fps = 4.16 @ muzzle (1315 ft-lbs KE) and 2.59 @ 500 yds (511 ft-lbs KE)
6.5 Grendel momentum for a 123gr SST BTHP load exiting a 16" barrel at 2390 fps = 5.81 @ muzzle (1560 ft-lbs KE) and 3.90 @ 500 yds (703 ft-lbs KE)
6.8 SPC momentum for a 120gr SST BTHP load exiting a 16" barrel at 2460 fps = 5.83 @ muzzle (1612 ft-lbs KE) and 3.61 @ 500 yds (619 ft-lbs KE)
6.8 SPC and 6.5 Grendel are within spitting distance of each other at those ranges, but 6.5 Grendel out paces the best 5.56 heavy match load by 28% @ muzzle and 34% @ 500 yds. 6.8 SPC bests it by 29% @ muzzle and 28% @ 500 yds. The difference in KE between 75gr 5.56 SM and 123gr SST 6.5 is +28% and only +18% for 120gr SST 6.8 by 500 yds.
The difference in momentum is greater than the difference in KE unless you go lighter. Penetration favors momentum bias, not KE bias and that's why 6.5 and 6.8 outperform 5.56 loads through intermediate barriers, which has been an ongoing issue with even the best 5.56 loads. Obviously bigger bullets leave bigger holes, so there's the terminal performance advantage in target as well.
5.56 loads can be lethal and there is absolutely NO question about that. However they are lethal for a fewer percentage of instances due to the inferior momentum, KE and fluid drag upon impacting the target (aka how much the tissue resists the bullet). While bigger bullets have higher resistance in flight (loss of KE and momentum is bad in this instance), they also have a higher resistance to traveling through the targets tissues (transfer of KE into the target, good in this instance). Balance is key and it seems from all of the research and actual testing that both 6.8 and 6.5 provide significant advantages without incurring significant increase in weight, loss of ammo capacity or changes to the platform.
They basically take the 7.62x39mm concept and optimize it for better medium range performance. 7.62x39mm performs great at short distances, but suffers some issues at intermediate ranges (250 to 500 yds). KE and momentum at the muzzle is comparable for 6.8, 6.5 and 7.62. But by 500 yds momentum for 7.62 has dropped to 2.51 for 123gr SST even if KE dump into the target at close ranges is better than 6.8 or 6.5. It's simply biased more for close range performance (less balanced). Consistency is the key!
These were taken from Brassfetcher and seem to correlate with the US military's testing in terms of 6.8 calibers producing better wounding than even 6.5 when passing through barriers:
2019-05-10 11_45_50-6.8mm SPC.jpg
2019-05-10 11_46_32-6.8mm SPC.jpg
2019-05-10 11_47_59-6.8mm SPC.jpg
Testing from multiple sources confirms this phenomenon. One would not think 0.3mm in diameter matters, but it seems to be the threshold where the increase in fluid drag is just enough provide better terminal performance on average. It's a trade off in slightly more KE / velocity loss at longer ranges vs. 6.5mm projectiles.
Sorry for the poor quality of the images (seems the forum downgrades the images), but here is the coloring of the lines and what loads they represent:
Blue line is .223 Remington Federal 55gr TSX
Red line is 6.5mm Grendel 120gr TSX
Green line is 6.8mm SPC 110gr TSX
Purple line is 50 Beowulf 325gr Gold Dot
All three intermediate calibers are using the same solid copper monolithic projectile from Barnes which is about as comparable as you can get in terms of bullet construction. Notice how consistent the 6.8 and Beowulf are, the two largest diameter projectiles (highest fluid drag in target).
The car door test in particular favors larger diameter projectiles while bare gelatin and auto windshields they all perform admirably. Not much more for me to say at this point which I'm sure your sick of reading, but at least I have presented some highly reputable data back up my choice and why I found 6.8 slightly more favorable than 6.5 and why both are highly favorable to 5.56 or 5.45.
Last edited by win&legend; 03-12-20 at 08:36.
Senior Member
Are there any lowers other than the Six8 that can accommodate 6.8 PMAGs? And can a magwell that size still take a 5.56 mag? Just curious.
Those who beat their swords into plowshares will plow for those who do not.-Ben Franklin
there’s some good in this world, Mr. Frodo. And it’s worth fighting for.-Samwise Gamgee
Senior Member
Mad Dog Weapons (mentioned already as the marketer of 277 WLV and the GPC cartridges) was working on an intermediate lower based off the Six8. He was also working on a metal magazine that allowed for longer than 2.26" oal. Not sure where that project is or if it is even in the works anymore.
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“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter cannot be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles."
Member
No, the six8 magwell is longer and wider a 5.56 mag will not work.
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Many years ago, I came very close to buying a Wilson Combat upper in 6.8 SPC for the purposes of hog hunting. However, I wound up buying a SCAR 17s instead for $2450 way back in 2012. It may be heavier than a 6.8 AR, but I find it hard to want to down size from a 7.62 NATO rifle that runs a suppressor well. It also allows me to simplify caliber choices I have on hand, and I can pretty much use it for everything (Heavy Metal matches, carbine classes, etc).
I think it’s a shame the military is using the 6.8 concept in a different cartridge. It would have been cool to see the 6.8 SPC adopted.
Member
I must be part of the old guard now...
I have an originally purchased 6.8 upper build from Tim Hicks/Kotonics that I run C-Products and PRI mags through. Boringly, consistently great accuracy from 90-115 grains (haven't tried anything else), and MANY very dead, one shot bucks taken on it. I reload for it using Ramshot X-Terminator. GREAT caliber.
Where violence is the local language, be fluent.
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