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Thread: 6.8 spc twist rate?

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    6.8 spc twist rate?

    First let me compliment everyone on a great forum. I'm new here be but ya'll seem to be the most knowledgable people I've seen about buliding AR's. I plan to build a 6.8 spc on a RRA frame. I have an RRA ATH carbine now that I really like alot. I plan on building the 6.8 the same. I want to use it for hunting and target shooting. My question is what barrel and twist rate would ya'll recommend? I've seen 1/'10 to 1/11 and 1/12. I want to build it with an 18" match spec II chamber. I plan on reloading some 110gr Accubonds for it. Thanks ahead of time for all the help! http://www.rockriverarms.com/index.c...ategory_id=526
    Last edited by Denny2277; 12-27-11 at 21:16.

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    1 in 11, 4 groove. Allows for high pressure loads like SSA combat (tactical) loads with no problems

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    This helped me out a ton when looking into 6.8. Has a lot more info in case you needed to know anything else.

    http://www.weaponevolution.com/forum...6.8-SPC-Guide.

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    Quote Originally Posted by avmech View Post
    1 in 11, 4 groove. Allows for high pressure loads like SSA combat (tactical) loads with no problems
    Which manufacturers sell that configuration?

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    Quote Originally Posted by NavArch View Post
    Which manufacturers sell that configuration?
    It's in the link I posted but here's a link to the barrel chart.
    There's better twist and barrel groove specs than those but they only provide marginal gains in performance.
    Just depends on what you want to get out of it and what you're looking to spend.

    Bison Armory is probably the best bet as far as 1:11 and four groove.
    They're also decently priced in comparison to the others and you can get them bead blasted or gunkoted.


    http://https://spreadsheets.google.com/pub?key=tOtyqlb35yLitvWlWWajZyg&output=html
    Last edited by nanners83; 12-28-11 at 09:10.

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    Thanks for the research

    The table you developed implies a ton of research work.

    Now, at the risk of appearing to be rude, I need to ask a question. Why should my next AR be a 6.8 SPC? I don't hunt. The carbine would be for SD, which implies a serious level of practice, and cheap ammo options just aren't out there. Reloading every shot I take can get a bit old. This is a serious, neutral question. Inputs are requested.

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    Quote Originally Posted by NavArch View Post
    The table you developed implies a ton of research work.

    Now, at the risk of appearing to be rude, I need to ask a question. Why should my next AR be a 6.8 SPC? I don't hunt. The carbine would be for SD, which implies a serious level of practice, and cheap ammo options just aren't out there. Reloading every shot I take can get a bit old. This is a serious, neutral question. Inputs are requested.
    You probably shouldn't. I run a 5.56 for training and self defense and a 6.8 for hunting. Given the right ammo the 5.56 will do just fine in a fight.

    The 6.8 does offer considerably better terminal petformane especially when barriers are involved. But terminal performance is meaningless if you cannot hit your target, that is where training (and lots of ammo) comes in. I guess the other option is to setup two identical rifles (one 5.56 and one 6.8) and train with the 5.56 and save the 6.8 for serious use.

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    If you already have a 5.56 just use that for the majority of your practice. Of course run some 6.8 also, but the majority can be the 5.56.

    You can even put the 5.56 upper on your 6.8 lower so controls and trigger will be the same.

    Don't let the cost of ammo be the only point you use to make a decision about which caliber to go with.

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    Quote Originally Posted by NavArch View Post
    The table you developed implies a ton of research work.

    Now, at the risk of appearing to be rude, I need to ask a question. Why should my next AR be a 6.8 SPC? I don't hunt. The carbine would be for SD, which implies a serious level of practice, and cheap ammo options just aren't out there. Reloading every shot I take can get a bit old. This is a serious, neutral question. Inputs are requested.
    The links I posted up are just stuff I found on google when I was researching the cartridge.
    I don't want want to take credit for others work.

    If you're not planning on hunting I would probably just stick with 5.56.
    I have not gotten the chance to hunt anything other than dove but was so impressed by the performance of 6.8 that I chose to get one in case I ever got the chance to go.
    The advantage of it over 5.56, as far as effective range and terminal ballistics, is pretty impressive considering that it is similarly priced for the same quality of ammo.

    Here's some more info comparing a few different calibers.
    http://68forums.com/forums/showthrea...l=1#post138642

    It's a great caliber just not for plinking yet. I think I remember reading that wolf maybe coming out with some 6.8 next year but I could be wrong.
    Last edited by nanners83; 12-28-11 at 23:37.

  10. #10
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    I believe it's Tula that said they would have 6.8 ammo in 2012... We'll see.
    I built mine to hunt with but didn't see anything to shoot with it this year. (sigh) Maybe next year.
    I like it better than the 5.56 (I have 4) but both calibers work with cheaper ammo cost for the 5.56. However, when you get premium ammo for the 5.56 the costs are about the same.

  11. #11
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    Spent 6.8 shell casings can also be sold to reloaders for a nice premium anywhere from $.30 to $.40 per case reducing your cost per round.

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    Denny,
    We offer 6.8 SPECII 18" barrels with 1/11" twist....

    http://shopwilsoncombat.com/68-SPC-II/products/396/
    Often Imitated-NEVER Duplicated
    Wilson Combat Online Representative
    m4carbine.net SITE SPONSOR
    www.wilsoncombat.com
    http://blog.wilsoncombat.com/
    Sales/Service (800) 955-4856

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    Nice, I'll be putting in my order for the 18" very soon. I handload, so what kind of performance can I expect with a 110gr Accubond with the 18" Recon Tactical? I see that it has the 6 grove.

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    Quote Originally Posted by sqwerl View Post
    Spent 6.8 shell casings can also be sold to reloaders for a nice premium anywhere from $.30 to $.40 per case reducing your cost per round.
    Thanks everyone for your help. I'll be moving along very soon on this project. I'll keep ya'll posted.

  15. #15
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    Denny,
    Our factory load 110gr BTHP runs 2700fps out of a 16" barrel. I haven't personally loaded the 110 Accubond for an 18" barrel, but I would think you could be in the 2700+ range with that bullet. If you are looking for a deer/hog hunting load, be sure to look into the Barnes 95gr TTSX.
    Often Imitated-NEVER Duplicated
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    www.wilsoncombat.com
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  16. #16
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    When we started testing the 6.8 in 06 I tried 10, 11, 12, and 13 twist. I could get unreal velocities out of the 13 twist using 85 and 90 gr bullets but the longer 120 and 130gr would not stabilize. I went to a 12 twist 3 groove that just barely stabilized the longer 130gr bullets. Tim and I had talked about having GS customs make 2 99gr bullets that were as long as possible and still fit in a PRI mag to increase the BC. Knowing those were coming we settled on a 11.25 twist 5R that will handle any 6.8 bullet that will fit in a PRI mag OAL 2.3"
    In short depending on the velocity a 12 twist may or may not stabilize the longest 120 and 130gr bullets or the 99gr GS custom bullets.

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