What's the low down on the 6.8?

[alamo5000]

Sorry guys, I haven't been participating in the forum a lot lately. I lurk but have been preoccupied with other things.

I recall reading a while back that the military is looking to adopt some form or another of 6.8 for SBR applications. It was all over the news so it was hard to miss.

I did a little bit of homework and from the looks of it a 6.8 in supersonic SBR applications should get more grain weight moving faster down range compared to 5.56. Compared to 300 BLK it still gets better marks on a down range energy scale when compared to say a 110 grain round when both are fired from similar length barrels. That impression [not verified information] is based on the basic stuff I've found online about it which honestly isn't a lot.

Anything you know about this please dish the dirt and let me know.

In 5.56 say out of a 10.5" SBR if the soft target is within 50 yards and you are shooting say 75 or 77 grain rounds, it's bad ass. That said the 5.56 is sort of ammo specific for that application.

In 300 BLK shooting 110 grain or 125 grain supers are pretty bad news as well out to 100 yards or more. I certainly would not want to get shot with it. I haven't done the math to figure out the energy.

The 6.8 seemingly out performs both though [or so I've heard] in supersonic SBR applications but again I have not done the math.

The other questions I have are which cases are they going to use [the military]? There are several 6.8 variants out there.

Other things to note, I think for quiet shooting 300BLK still has a slight leg up for AR platforms. 5.56 performs best out of longer barrels. The lack of bullet mass and loss of velocity in an SBR knock off a lot of performance.

How much better a 6.8 SBR would be shooting supersonic rounds than a 300 BLK shooting light supersonics I don't know.

If this is going to get official support of the US Government then it is definitely something I would consider building an upper for or even building a whole new SBR for.

[Uffdaphil]

I just ordered the last parts for a 6.8SPC 12.5” build. Was going to do a 6.5 Creed, but decided against for several reasons. First the 6.8 is small frame - lighter. Second much cheaper as I already had many of the parts in my AR-15 stash. Third my old eyes are never going to like extreme long ranges. And the biggest is that Sulzer has an upper/lower combo designed for 6.8 pmags at half the price of LWRC’s.
http://sulzerfirearms.com/mk1-spc-receiver-set-magpul-6-8spc-mag-compatible/


Whether 110 grain supers are better in 6.8 than .300BLK I don’t know. The guys on the 68 forum think so, but I love the BLK for near Hollywood quiet with subs from an 8-9” bbl. I expect the 6.8 longer bbl will have better velocity with supers and be smoother with the mid-gas.

[Joelski]

Looks like a New Frontier set, UDF. Their billet receivers are definitely bomb-proof.

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[Joelski]

BTW, I read somewhere (mil times?) that the round the military is looking at is nothing like the current crop of 6.8 ammunition. They are pretty hung up on the "next gen caseless" prospect.

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[GriffonSec]

I love my 6.8 SBR. Mag options would be wonderful, but I'm married to that Noveske lower now.

JerryR and I chrono'd several grain loads through several barrel lengths in 8.5", 10.5" and 16". I'll hit him up and see if he'll post that chart back up. 85 and 90 grain did best through the shorty, but 100 and 110 weren't shabby, and 120 was interesting.

Expensive to shoot though, damn!

[FortTom]

BTW, I read somewhere (mil times?) that the round the military is looking at is nothing like the current crop of 6.8 ammunition. They are pretty hung up on the "next gen caseless" prospect.

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Read the same thing. First I was excited, because I just recently put the finishing touches on my 16", but only the caliber is the same. Totally different round.
I thought 6.8 would be flowing like 5.56, but they just wanted a heavier hitting round and landed on the 6.8 bullet.

FT~

[Jerry R]

http://www.weaponevolution.com/forum/attachment.php?attachmentid=6002&d=1543002294
http://www.weaponevolution.com/forum/attachment.php?attachmentid=6003&d=1543002306
http://www.weaponevolution.com/forum/attachment.php?attachmentid=6004&d=1543002316

[GriffonSec]

^^ That's it, thanks!

[alamo5000]

BTW, I read somewhere (mil times?) that the round the military is looking at is nothing like the current crop of 6.8 ammunition. They are pretty hung up on the "next gen caseless" prospect.

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Caseless? What? I am in new turf here. What in the hell is a caseless round?


I love my 6.8 SBR. Mag options would be wonderful.... 85 and 90 grain did best through the shorty, but 100 and 110 weren't shabby, and 120 was interesting.

Expensive to shoot though, damn!

Mag options? You can't run standard mags with a 6.8? Looks like the OAL is about the same as 5.56 but I could be wrong.

I ran the numbers for a generic 85 grain at the velocities on Jerry's chart and wow. That's substantial. Compared to 75gr TAP out of a 10.5 that's more than 400 ft/lbs more energy at 100 yards. The 100 yard energy is more than getting hit with a 55gr 5.56 out of a 16" barrel at point blank.

Just imagine if they come up with some lehigh defense extreme whatever bullets for the 6.8. That would make that thing messy in good way.

BTW is it expensive because of components or are you running loaded commercial ammo?


Read the same thing. First I was excited, because I just recently put the finishing touches on my 16", but only the caliber is the same. Totally different round.
I thought 6.8 would be flowing like 5.56, but they just wanted a heavier hitting round and landed on the 6.8 bullet.

FT~

We had similar thoughts. Those rough numbers I got from the 85gr data are very impressive though. Dayum.


And thanks Jerry for the charts!!! That helps a ton!

[Joelski]

Caseless? What? I am in new turf here. What in the hell is a caseless round?

Textron is one of the suppliers that's already got a working replacement for the SAW. The caseless ammo has the round encased in the propellant, housed in a thin polymer coating to contain it all. The effort is being made to make ammo lighter while increasing the ammunition load the operator can carry.

Center is the equivalent of 7.62 without the brass nonsense.

https://i.pinimg.com/originals/cc/4f/a2/cc4fa2490840ece7be6804b616a4b84a.jpg

[Joelski]

Correction: The Textron is using a 6.5 mm projectile in a polymer case.

https://www.thefirearmblog.com/blog/wp-content/uploads/2016/09/IMG_0249-660x370.jpg

[alamo5000]

Textron is one of the suppliers that's already got a working replacement for the SAW. The caseless ammo has the round encased in the propellant, housed in a thin polymer coating to contain it all. The effort is being made to make ammo lighter while increasing the ammunition load the operator can carry.


What's that on the bottom? [In your attachment]

I've seen some polymer cased ammo before and it works by all accounts told to me. I've never shot any.

If they are going to make the new 6.8 SBRs to shoot polymer case ammo then just going ahead and going with a 6.8 SPCII or something like that would still get it done.

I know there are a lot of different current 6.8 rounds but I am not sure the difference, or cost, or brass availability etc.

[Aragorn]

I thought caseless ammo induced heat problems earlier than cased ammo during long periods of fire, as none of the heat generated was 'extracted' from the chamber as with spent casings.

I'd be interested to see how they get around that.

[GriffonSec]

Mag options? You can't run standard mags with a 6.8? Looks like the OAL is about the same as 5.56 but I could be wrong.


BTW is it expensive because of components or are you running loaded commercial ammo?




You're limited to 6.8 specific mags (case is larger). Barrett ($38 on sale), PRI ($35) and C-Products (15-20) off the top of my head. The Magpul 6.8 mags are sized different and when they came out, were specific to LWRC receivers, they won't fit a standard receiver. You can use a standard mag, but cannot load anywhere near full capacity, it'll swell. I've had no issues with C-Prod, but others say they have.

Yes, factory loaded ammo. 90 gr Federal is fairly cheap, but that 85 gr Barnes loaded was 36 a box at the time that chart was done. I've stocked up on 90, and haven't picked up any Barnes since then. Next trip Jerry makes it up, we'll have to add the 90gr to that chart. IF I were a reloader, I'd likely load 85gr, but still gotta have the brass.

FWIW, Abrams tanks have had basically caseless ammo forever, just an end cap after firing. Caseless small arms would be interesting.....


On Edit, Based on bullet performance, and me getting older and fighting the red-dot, I opted to try the 1-8x scope, which I like quite a bit. Put it on a bit of a diet to get the weight back down to the same as with the H1.

https://farm5.staticflickr.com/4840/45306002394_47f95fea7c_b.jpg (https://flic.kr/p/2c2x75j)68 sbr redo 3 (1 of 1) (https://flic.kr/p/2c2x75j) by Steven Ragan (https://www.flickr.com/photos/111961163@N05/), on Flickr

[Big_Tom]

I have been wanting to get in the 6.8 game for a while. Started the new build and have been looking for a 18" barrel that has been machined to work with Ops Inc brakes and collars.

I found one a Bison Armory at a decent price. But they have redone the chamber from a 6.8spc II to the "bison chamber" here is a description of this chamber.

https://68forums.com/forums/showthread.php?112850-New-6-8-Bison-Chamber&amp=1

I wanting this to be a MK12 style build and be able to use it hunting deer and hog out to about 300yds.

Does anyone recommend going with a different caliber like 6.5g?

Didn't mean to hijack the thread Alamo.

Tom


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[BoilerUp]

I have been wanting to get in the 6.8 game for a while. Started the new build and have been looking for a 18" barrel that has been machined to work with Ops Inc brakes and collars.

I found one a Bison Armory at a decent price. But they have redone the chamber from a 6.8spc II to the "bison chamber" here is a description of this chamber.

https://68forums.com/forums/showthread.php?112850-New-6-8-Bison-Chamber&=1

I wanting this to be a MK12 style build and be able to use it hunting deer and hog out to about 300yds.

Does anyone recommend going with a different caliber like 6.5g?

Didn't mean to hijack the thread Alamo.

Tom


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The two 6.8 barrel makers with good reputations for accuracy (Bison and ARP) have both tweaked the chamber of their barrels, essentially creating a .233 Wylde like option for the caliber. So, I say buy that Bison barrel with confidence. If you weren't concerned about the ops collar, I'd probably try to steer you to the ARP barrel ( https://www.ar15performance.com/inc/sdetail/38010/43898 )

I'll try to avoid turning this into 6.8 SPC vs 6.5 Grendel thread by saying that either will get the job done and you'd be well served by the 6.8 SPC for your intended application. One caveat with the 6.8 SPC is you really need to hand load to achieve the full potential due to Remington's botched SAAMI spec that all the all factory ammo is loaded to. It's still a great round even with factory ammo, but you can easily squeeze more juice out of the round if you load. Avoid barrels built to the SAAMI ("SPC I") spec.

Back to the OP...

I'm a big fan of the 6.8 SPC in the AR. I think it's a great intermediate cartridge. I've got two. Out of a suppressed 12.5" barrel shooting 100 gr Accubonds I was getting around 2,620 fps at higher charges although the best accuracy appears to be around 2,550fps (28.5gr of AA2200) which is about where my SSA Factory rounds clock in. That seems to jive well with Jerry's data above.

One of the things I like about the 6.8 SPC is it performs very well out of short barrels. Bullet selection in .277 is pretty good, too.

I think the main 6.8mm option (wildcat) is the 277 Wolverine which is based on .223 cartridge so will have less case capacity. Folks do shoot the 6.8 subsonic, but if you are going to cripple the round that much you might as well stay with the 300 AAC or get a PCC, IMO.

Comparing supers, putting the 300 AAC up against the 6.8 SPC isn't even a fair fight. The case capacity of the 6.8 lets you push that round in ways the Blackout was never intended.

[Big_Tom]

The two 6.8 barrel makers with good reputations for accuracy (Bison and ARP) have both tweaked the chamber of their barrels, essentially creating a .233 Wylde like option for the caliber. So, I say buy that Bison barrel with confidence. If you weren't concerned about the ops collar, I'd probably try to steer you to the ARP barrel ( https://www.ar15performance.com/inc/sdetail/38010/43898 )

I'll try to avoid turning this into 6.8 SPC vs 6.5 Grendel thread by saying that either will get the job done and you'd be well served by the 6.8 SPC for your intended application. One caveat with the 6.8 SPC is you really need to hand load to achieve the full potential due to Remington's botched SAAMI spec that all the all factory ammo is loaded to. It's still a great round even with factory ammo, but you can easily squeeze more juice out of the round if you load. Avoid barrels built to the SAAMI ("SPC I") spec.

Back to the OP...

I'm a big fan of the 6.8 SPC in the AR. I think it's a great intermediate cartridge. I've got two. Out of a suppressed 12.5" barrel shooting 100 gr Accubonds I was getting around 2,620 fps at higher charges although the best accuracy appears to be around 2,550fps (28.5gr of AA2200) which is about where my SSA Factory rounds clock in. That seems to jive well with Jerry's data above.

One of the things I like about the 6.8 SPC is it performs very well out of short barrels. Bullet selection in .277 is pretty good, too.

I think the main 6.8mm option (wildcat) is the 277 Wolverine which is based on .223 cartridge so will have less case capacity. Folks do shoot the 6.8 subsonic, but if you are going to cripple the round that much you might as well stay with the 300 AAC or get a PCC, IMO.

Comparing supers, putting the 300 AAC up against the 6.8 SPC isn't even a fair fight. The case capacity of the 6.8 lets you push that round in ways the Blackout was never intended.Yeah ARP was the first placed I looked into about barrels. I've heard really great things about them. I haven't gotten into reloading yet so I'll be sticking to factory till then. And I'm not planning on shooting it over 500yds at the range anyways. That's why I really don't want a 6.5g cause I won't really be using it for the really long stuff. Thanks for the reply.

Tom

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[alamo5000]

You're limited to 6.8 specific mags (case is larger).

IF I were a reloader, I'd likely load 85gr, but still gotta have the brass.

Caseless small arms would be interesting.....



Well that sucks. The brass won't flow and no telling how much it costs. You need special mags. And apparently it's expensive to shoot. The gain for an SBR though is impressive. With the right bullet that thing seems like it would pack a wollop.



Didn't mean to hijack the thread Alamo.



Don't sweat it. We are all here to learn a little something.




I'm a big fan of the 6.8 SPC in the AR. I think it's a great intermediate cartridge. I've got two. Out of a suppressed 12.5" barrel shooting 100 gr Accubonds I was getting around 2,620 fps at higher charges although the best accuracy appears to be around 2,550fps (28.5gr of AA2200) which is about where my SSA Factory rounds clock in. That seems to jive well with Jerry's data above.

One of the things I like about the 6.8 SPC is it performs very well out of short barrels. Bullet selection in .277 is pretty good, too.

I think the main 6.8mm option (wildcat) is the 277 Wolverine which is based on .223 cartridge so will have less case capacity. Folks do shoot the 6.8 subsonic, but if you are going to cripple the round that much you might as well stay with the 300 AAC or get a PCC, IMO.

Comparing supers, putting the 300 AAC up against the 6.8 SPC isn't even a fair fight. The case capacity of the 6.8 lets you push that round in ways the Blackout was never intended.

I am not that familiar with the Wolverine. I don't know what kind of velocities that will generate.

As for comparing with 5.56, 300 BLK, and 6.8... there is clear dominance from the 6.8 when it comes to flat out energy. Some people still don't like 300BLK but from my perspective with the right ammo it can be very effective. The ability to go really quiet is very nice. Terminal performance if you shoot light pills is still not bad at all. 5.56 if you are shooting say 77gr rounds is still going to do nasty things especially inside of 50 yards.

On balance 5.56 is nice because ammo is available--as is brass. You can get 77 gr bullets for reloading or even factory ammo for not so much relatively speaking. There is just a lot of support there for it. Downside is beyond 50 yards you are taking your chances and it's probably not the best choice for say hog blasting.

300BLK is good if you shoot light weight supers and it's versatile enough where you can keep it very quiet. More expensive to shoot though.

6.8 technically has a lot more performance [again talking only about SBR performance] but the cost advantage and support are not there. That said it definitely opens up the door to have a seriously good hog blasting machine.

I guess they all have their pros and cons.

[GriffonSec]

I wouldn't have built a full size non NFA 6.8. I wanted a specific defensive gun, and the 6.8 in SBR fit the bill for me in spades. In hindsight, I might have gone 10.5 instead of 8.5, but I'm quite satisfied.

If you reload, you can pick up S&B 110 and Federal white box 90s for around 12-14 a box when on sale. I think best price I've gotten was 11 a box. Makes it cheap enough and worth crawling for brass. Then you can start cooking your own load up. I use 110 on the range, and the brass seems good enough. Just don't use Remington, large primers. Every thing else is small primer.

[UWone77]

This has been an informative read.

I was going to do a 6.8 build if/when Rainier decides to do a 6.8 Ultramatch.

But it seems like 6.8 isn't really worth it unless you load your own ammo.

Thanks gents.

[alamo5000]

This has been an informative read.

I was going to do a 6.8 build if/when Rainier decides to do a 6.8 Ultramatch.

But it seems like 6.8 isn't really worth it unless you load your own ammo.

Thanks gents.

The reloading components alone for an 85 grain round would cost .60 to .70 cents per round. I reload and I like to do it, but damn that's still pretty high.

[BoilerUp]

The reloading components alone for an 85 grain round would cost .60 to .70 cents per round. I reload and I like to do it, but damn that's still pretty high.


Brand new starline brass is 40 cents, so if you only get four firings, that's 10 cents for the brass, ~11 cents for 25 grains of powder, and 4 cents for the primer. That gets you to 25 cents w/o the bullet, which can range from 20 cents for plinkers to 68 cents for Barnes. The only big difference between that and 300 AAC is the 6.8 takes twice as much powder and I guess you can convert the brass from surplus 1F 5.56. Loading Barnes is expensive in any caliber (I just ordered some Barnes TAC-TX 110s for my 300).

For cost efficient 6.8 loading, I recommend buying the S&B 110 FMJ for $12.95 a box (https://www.sgammo.com/product/sellier-bellot/20-round-box-68-spc-110-grain-fmj-sellier-bellot-ammo-sb68c ) to get amazingly accurate FMJ ammo and great brass that doesn't have crimped primers. For plinking, reload with Hornady 110gr BTHP at 22 cents. For hunting, choose Accubonds, Barnes, Gold Dots (buy factory Fusion or XM68GD pulls if you can find them), or SST. Accurate 2200 seems to be the go-to powder. There are some deals to be had. The military contract 90 gr Gold Dot pulls are hard to come buy now, but things like this still pop up: https://www.rmrbullets.com/shop/bullets-for-reloading/bullets-for-reloading-277-6-8mm-18/6-8-277-115-grain-nosler-custom-competition-bthp/#reviews

Note that 6.8 SPC is the only alternative AR caliber with military adoption, thanks to the Saudis and their LWRC Six8s for the Royal Guards (http://silahreport.com/2018/01/24/guarding-the-malikah-lwrc-uwic-carbines-of-the-saudi-royal-guard-regiment/ ). I picked up quite a bit of the excellent Federal XM68GD (90 grain Gold Dot, white box) for pretty cheap as contract overrun, but that's dried up. Hopefully the Saudis will order some more some time, but you can buy the round now as Federal Fusion marketed for hunters. I get sub-MOA out of both the XM68GD and the S&B 110gr FMJ from my 16" ARP barrel (and I believe I was right at 1MOA with the 110 gr Fusion). While the round does benefit "more than average" from reloading, the factory ammo does still perform well and there are some excellent options. PPU recently entered the game, too, finally. I'm just now getting it to working up loads now that I've got my 12.5" suppressed SBR setup completed.

[alamo5000]

Brand new starline brass is 40 cents, so if you only get four firings, that's 10 cents for the brass, ~11 cents for 25 grains of powder, and 4 cents for the primer. That gets you to 25 cents w/o the bullet, which can range from 20 cents for plinkers to 68 cents for Barnes. The only big difference between that and 300 AAC is the 6.8 takes twice as much powder and I guess you can convert the brass from surplus 1F 5.56. Loading Barnes is expensive in any caliber (I just ordered some Barnes TAC-TX 110s for my 300).


I can't say that I have researched out 6.8 reloading components in any detail so I am sure you could get into it a lot cheaper. If that's the case then I will obviously keep it in contention.

I would just have to think what I would get in return, which would be a nice SBR pig hunting rig that can knock em down.

Truth be told that same thing is one of my frustrations with 300BLK. Getting heavy bullets in bulk is kind of pissing me off. Once my personal economic situation improves I will do whatever I can to just buy bullets in bulk and get like 10,000 of them in one shot. I can't afford to do it now but eventually that's on my list. The good thing (I guess) about 300 BLK is I have options to just shoot the hell out supers and I can find some lighter weight bullets in bulk.

If I did get into something like 6.8 before I ever did it I would probably buy the holy shit out of some brass and maybe some bullets and do the same thing. Just buy like 5000 pieces of new good brass and if I find a good bullet do the same.

Basically I am of the belief that having a cool gun in a great caliber is one thing, but having no ammo for it is another. When opportunity arises I am kind of hoarder when it comes to stuff like that.

[Big_Tom]

Now since I do have a SBR'd lower I may just build the MK12 up in 5.56 and build a upper for the lower. And it might dive me a reason to get the new SB pistol brace.

What is a good length for barrel? I've been seeing 12.5"



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[BoilerUp]

Now since I do have a SBR'd lower I may just build the MK12 up in 5.56 and build a upper for the lower. And it might dive me a reason to get the new SB pistol brace.

What is a good length for barrel? I've been seeing 12.5"



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The ARP 12.5 barrel is very popular as it doesn't give up too much from the carbine and retains mid-length gas. ARP now sells a 10.5" and I personally wouldn't go shorter than that. Wilson Combat has an 11.3" (on sale right now, too), that would probably be good.