Another 6.8 build question, please

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  • Capt Skup

    Ultimate Member
    Feb 29, 2012
    2,385
    Calvert County
    I have a couple of Anderson lowers I am thinking of building up. One I am thinking of using for a 6.8 rifle. Please be kind to share your knowledge on a budget 6.8 build, for I have questions to ask. First:
    1. Can a common AR lower be used for the 6.8?
    2. Does Magpul market 6.8 magazines? ( 5.56 mags will not work with the 6.8, is that correct?).
    3. Can the AR upper, normally sized for the 5.56, work with the 6.8?
    4. Is there anything else different besides the barrel and BCG?
    Thank you for your responses, and please share any ideas for a budget build rifle.
     

    jrumann59

    DILLIGAF
    MDS Supporter
    Feb 17, 2011
    14,024
    I have a couple of Anderson lowers I am thinking of building up. One I am thinking of using for a 6.8 rifle. Please be kind to share your knowledge on a budget 6.8 build, for I have questions to ask. First:
    1. Can a common AR lower be used for the 6.8? 6.8SPC
    2. Does Magpul market 6.8 magazines? ( 5.56 mags will not work with the 6.8, is that correct?). Mags would need to be modified or you could buy dedicated though they may not be Magpul
    3. Can the AR upper, normally sized for the 5.56, work with the 6.8? sure if the ejection neess to be enlarged you can do that or you can buy an upper for 6.8 SPC but I think only the .450 to .50 calibers require larger ejection ports
    4. Is there anything else different besides the barrel and BCG? I am not 100% but it is possible that it may require a change in buffer weight and depening on the gas port in the barrel it will need a corresponding gas block
    Thank you for your responses, and please share any ideas for a budget build rifle.

    See bolded.
     

    jimbobborg

    Oddball caliber fan
    Aug 2, 2010
    17,112
    Northern Virginia
    Three differences: Barrel, bolt, and magazines. Everything else is interchangeable. Best bang for your buck upper is from Bison Armory. PRI mags make the best 6.8 magazines, but Barret makes the only real 30-round magazines for the caliber.
     

    KH195

    Ultimate Member
    Jan 10, 2013
    1,550
    Virginia
    Many companies make 6.8 uppers that fit on standard 5.56 lowers. Barrel, bolt (just the actual bolt... the bolt carrier, firing pin, etc. are all interchangeable with standard 556 components), and mag will be different and 6.8 specific as already mentioned...556 mags will NOT work with 6.8. Magpul does make 6.8 Pmag magazines, BUT they are proprietary to only the LWRC Six8 platform of rifles, which uses a lower of different dimensions (so the 6.8 pmags will NOT fit in a standard AR 5.56 lower). I have a 6.8 SBR, also an LWRC but the older M6 generation that uses a standard 5.56 lower. I've had the best luck with the newish C-Products Defense 28 round 6.8 mags which have been flawless in my particular gun (they are more curved almost like an AK mag based on the shape of the 6.8 case). I've also heard the Barret 6.8 mags run well. 6.8 is a great round and performs especially well in short barrels. If you have any more questions feel free to hit me up!
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    I am surprised you're not considering 6.5 Grendel, OP. What attracted you to 6.8 SPC over 6.5G?
     

    davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    224 valk is also an option with a 6.8 bolt. as noted above, barrel (of course), bolt and mags are different from ar-15/5.56/.223.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Ignoring the probable-bias of the source, most of the arguments in that thread are totally inane or reference problems Grendel had years ago that have been resolved.

    The only two arguments I thought had any merit at all:
    1.6.8 SPC II has 3K higher max chamber PSI and has a .013 larger bullet diameter... that's not exactly compelling stuff in terms of enhanced short-range performance.
    2. Better hunting bullet selection. Possibly true, just unsure whether there's some hunting bullet that exists for 6.8 that's just significantly better than anything out there for 6.5G.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Ignoring the probable-bias of the source, most of the arguments in that thread are totally inane or reference problems Grendel had years ago that have been resolved.

    The only two arguments I thought had any merit at all:
    1.6.8 SPC II has 3K higher max chamber PSI and has a .013 larger bullet diameter... that's not exactly compelling stuff in terms of enhanced short-range performance.
    2. Better hunting bullet selection. Possibly true, just unsure whether there's some hunting bullet that exists for 6.8 that's just significantly better than anything out there for 6.5G.

    IMHO, in part with the success of 6.5 Creedmoor I suspect a better bullet selection for 6.8 is either not really true, or is a bit like there are more options in mid sized sedans than there are in small sedans. News ash, there are a ton.

    Neither is ever likely to touch .30 caliber bullet selection. But both have great options. There isn’t much in factory chambered 130gr in 6.8. And that is more of an issue if you aren’t going to reload as 110gr 6.8 has pretty bad medium and long range performance compared to the typical 120/123gr 6.5 Grendel loadings.

    I mean, it isn’t actually terrible, but 6.5 Grendel pulling ahead of 6.8spc past 400yds is predicated on typical 123gr 6.5 Grendel loadings vs a “typical” 130gr 6.8spc loading. Which is hard to find.

    110gr 6.8 vs 123gr 6.5 and the 6.5 pulls ahead at more like 200 or 250.

    Which for typical hunting ranges, still makes 6.8 better. But let’s also be frank, 6.5 Grendel is also plenty fine against medium game and both 6.5G and 6.8SPC really aren’t suitable for something big like elk, moose or bear.

    6.5G is suitable for long range target shooting and 6.8 just plain isn’t. 6.8 is a little better with typical loadings to about 200yds, maybe 300 for hunting. 6.8 has a hair more mag capacity (27 vs 25). If you reload your own, 6.8spc uses about 10% more powder for typical loadings and that slightly higher pressure also means case life will be slightly lower.

    Really other than that medium to long range performance differential that gets to be substantial I think it is “what do you prefer”. Factory loadings there are a few more for 6.8SPC than 6.5G, but not a tremendous difference in them IMHO. And you’ll find 6.8SPC in more stores than 6.5G. Also 6.8SPC sometimes has sales on brass cased ammo that’ll run you $11-13 a box and Grendel is rarely that cheap (you can get 200 round ammo cans of 123gr HPBT with free shipping from Sportsman’s warehouse for $129.99 as the regular full price).

    6.5G has Wolf steel. If your gun likes it, great $5-8 a box steel. Mine doesn’t. It shoots 5-6MOA. I’ve tried several batches (it shoots Hornady all loadings at .9-1MOA and Federal 120gr fusion at .7MOA)

    That was part of why I built a Grendel instead of an SPC. That and my 18” can be used out to 1000yds with the right ammo. Barely stay supersonic that far, but it can be done. SPC it can’t be.
     

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