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  1. #1
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    What's the low down on the 6.8?

    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.

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    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-re...ag-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.
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  3. #3
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    Looks like a New Frontier set, UDF. Their billet receivers are definitely bomb-proof.

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    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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    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!

  6. #6
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    Quote Originally Posted by Joelski View Post
    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.

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  7. #7
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    NRA Benefactor Member
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  8. #8
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    ^^ That's it, thanks!

  9. #9
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    Quote Originally Posted by Joelski View Post
    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?

    Quote Originally Posted by GriffonSec View Post
    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?

    Quote Originally Posted by FortTom View Post
    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!
    Last edited by alamo5000; 23 November 2018 at 18:17.

  10. #10
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    Quote Originally Posted by alamo5000 View Post
    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.

    Last edited by Joelski; 23 November 2018 at 18:28.
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  11. #11
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    Correction: The Textron is using a 6.5 mm projectile in a polymer case.

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  12. #12
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    Quote Originally Posted by Joelski View Post
    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.
    Last edited by alamo5000; 23 November 2018 at 18:51.

  13. #13
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    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.
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  14. #14
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    Quote Originally Posted by alamo5000 View Post



    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.

    68 sbr redo 3 (1 of 1) by Steven Ragan, on Flickr
    Last edited by GriffonSec; 24 November 2018 at 09:38.

  15. #15
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    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/showthre...-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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