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Thread: 6.8 SPC EDUCATION THREAD......Tell what you...&..Ask Questions

  1. #1

    Default 6.8 SPC EDUCATION THREAD......Tell what you...&..Ask Questions

    Let us do a 6.8 Special Purpose Cartridge Thread........Please ask questions......Please help educate members like me. with what you know or useful links.

    This is the most useful link I have found: http://www.ar15.com/forums/t_3_121/350804_.html

    AND: http://www.ar15.com/forums/t_3_12/353523_.html

  2. #2
    Member AKDoug's Avatar
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    There is an entire forum dedicated to the 6.8 SPC... www.68forums.com
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    Member GD Yankee's Avatar
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    Some interesting 6.8 info here:

    http://www.lwrci.com/articles/SGNLWRCsix8.pdf

    I tried but haven't yet found a good article discussing the evolution of the 6.8 chamber. It apparently makes quite a difference which chambering you have to get the most out of the cartridge.

    For several years I have considered getting a 6.8 upper, but I keep hoping the military is going to decide what they want. So far it hasn't made big inroads into either the 5.56 or the 7.62.

    The 6.8 is a cool round, but I would also consider either the 6.5 Grendel or the 300 Blackout as they both seem more popular than the 6.8 SPC.

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    Member Float Pilot's Avatar
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    Actually the best site for reading about the 6.8mm SPC is the 6.8mm Forum.

    http://68forums.com/forums/forum.php?

    I have fired about 3,000 experimental 6.8mm handloads through two rifles. A 16 inch carbine and a 24 inch rifle.
    The 16 showed that the 6.8 was a better combat round for two legged and maybe lighter game critters compared to the 5.56mm in the same barrel length.
    The 24 inch AR showed that it could be made into a descent medium range cartridge for medium game like caribou.

    Some examples of loads in the 24 inch Black Hole Weaponry Barrel.
    Using AA-2200 powder which so far seems to get the most velocity.


    AA-2200 powder in 24in BHW barreled AR
    Stag AR with 24 inch poly rifled Black Hole Weaponry Barrel
    12 power Pentex Scope.
    100 yards, rain, 12 knot winds, 42 degree F.

    All Loads SSA once fired brass. CCI 450 magnum primers (saving my military primers)
    Lee factory Crimp on all loads.
    Chronograph at 10 feet from muzzle.


    90gr Sierra HP
    31.5gr AA-2200
    2.219 in COL
    Vel= 3,265 fps and a 0.50 inch group
    Dirty necks , semi flat primers
    Muzzle Energy 2,130 foot pounds, point blank hunting envelope 285 yards.

    95gr Barnes TTSX
    31.0gr AA-2200
    2.230 COL
    Vel= 3,270 fps and a 1.0 inch group
    Dirty necks, semi flat primers
    Muzzle Energy 2,255 foot pounds, point blank envelope to 303 yards.
    Holds 1,000 foot pounds out to 375 yards.

    110gr Nosler Accubond
    29.0gr AA-2200
    2.260 col
    Vel= 3,020 fps and a 1.4 inch group
    Dirty case necks
    Muzzle Energy , 2,228 foot pounds, point blank hunting envelope to 290 yards
    Holds 1,000 ft pounds out to 425 yards.

    110gr Barnes TTSX
    29.0gr AA-2200
    2.280 col
    Vel= 2,990 fps and a 2.0 inch group
    dirty case necks
    Muzzle Energy 2,184 ft lbs, point blank envelope to 288 yards.

    130gr Sierra Soft Point flat base
    27.0gr AA-2200
    2.280 col
    Vel=2,658 fps and a 1.0 inch group
    Dirty necks
    Muzzle Energy 2,039 ft lbs. Point Blank hunting range of 263 yards
    Holds 1,000 foot pounds out to 425 yards.

    150gr Speer Soft Point Flat Base
    25.0gr AA-2200
    2.280 col
    Vel= 2,360 fps and a CLOVERLEAF HOLE
    dirty necks, semi-flat primers
    Muzzle Energy 1,855 foot pounds, Point Blank hunting range 237 yards
    Holds 1,000 ft lbs out to 375 yards
    Floatplane,Tailwheel and Firearms Instructor- Dragonfly Aero
    Experimental Hand-Loader, NRA Life Member
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  5. #5

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    WOULD someone be willing to convert these Velocities into "Foot Pounds"........Please.......Thank you.



    Velocity Differences of Bullet in Different Length Barrels

    SSA 2nd generation 115 gr SMK OTM w/cannelure, 5 shot averages:
    __________________________________________________ ___________
    __________________________________________________ ___________


    20” barrel: ave vel = 2561 fps; 10 fps extreme spread

    16” barrel: ave vel = 2525 fps; 18 fps extreme spread –– lost 36 fps from 20"

    12.5” barrel: ave vel = 2384 fps; 12 fps extreme spread –– lost 141 fps from 16"

    10” barrel: ave vel = 2265 fps; 27 fps extreme spread –– lost 119 fps from 12.5"

    7.5” barrel: ave vel = 2035 fps; 27 fps extreme spread –– lost 230 fps from 10"
    –––––––––––––––––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––––––––––––––––

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    Member AKDoug's Avatar
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    http://www.firearmexpertwitness.com/...s/calcnrg.html here you go. Enter your data.

    All I know is that those velocities are slow for a 6.8
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    The biggest challenge with the 6.8 Is that it was initially released by Reminington and they simply didn't do sufficient testing to find it's optimal configuration. They ran a to fast twist barrel and the original chamber didn't have enough throat. The SPCII chamber fixed this and is the most common chamber available today. In fact I am not aware of any manufacturer still cutting the original twist and chamber to include Remington. There are still variations in twist from 1:10 to 1:12 and my personal favorite is the 1:11.5 twist ARP barrels though lots of people are getting great results from the 1:12. The 1:10 barrels are fine as well but the upper limit will not be as high if you hand load.

    The biggest negative is the fact that Remington produced their original spec and sold them to people. If you have one it can be reamed to spec II easily but the ammo manufacturers are hesitant to sell full tilt ammo that will run fine in the specII chamber but would be to hot in the original. If buying a new or recent 6.8 there is really nothing to be worried about.

    I run a 16" carbine with a 1:11.5 twist and with Hornady 110 factory match I am in the 2600 fps range, unfortunately early in my testing last summer I tried to make the most of an afternoon with the sun fast dipping and put a round through my chrono effectively ending my testing for the year. Good news is the round has no problem penetrating about 2' of prochrono and was definitely a 1 shot kill.

    There is supposed to be Federal ammo available some time this year though I am a bit afraid that the ammo shortages and run on black guns may knock a hit on that. There are now countries ordering the 6.8 for M/LE uses and Federal has a large order of ammo to fill for that. It is expected that this production will eventually wind up providing a much cheaper source of brass and reasonably priced plinking ammo.

    At this time the future looks bright for the SPC now that a few die hard manufacturers have figured out how to get the original remington expectations out of the round. I feel it is about the best all around AR cartridge and competes favorably with the 6.5 grendel at most ranges with the benefit of being faster in a shorter barrel. We finally have AA2200 readily available now with 3 bears carrying it as well as others so getting the most out of it on the bench is pretty easy. I would not hesitate to use mine on caribou or even elk at closer ranges. It is a fantastic round for kids to learn on and has a lot more knockdown than a .223 without adding any significant recoil.

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    Quote Originally Posted by AGL4now View Post
    WOULD someone be willing to convert these Velocities into "Foot Pounds"........Please.......Thank you.



    Velocity Differences of Bullet in Different Length Barrels

    SSA 2nd generation 115 gr SMK OTM w/cannelure, 5 shot averages:
    __________________________________________________ ___________
    __________________________________________________ ___________


    20” barrel: ave vel = 2561 fps; 10 fps extreme spread

    16” barrel: ave vel = 2525 fps; 18 fps extreme spread –– lost 36 fps from 20"

    12.5” barrel: ave vel = 2384 fps; 12 fps extreme spread –– lost 141 fps from 16"

    10” barrel: ave vel = 2265 fps; 27 fps extreme spread –– lost 119 fps from 12.5"

    7.5” barrel: ave vel = 2035 fps; 27 fps extreme spread –– lost 230 fps from 10"
    –––––––––––––––––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––––––––––––––––
    1674 ft'lbs
    1627 " "
    1451 " "
    1309 " "
    1057 " "

    Info from http://www.reloadammo.com/footpound2.htm- just plug it in.

  9. #9

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    Thank You, Thank you very much

    Quote Originally Posted by AKBEE View Post

    1674 ft'lbs
    1627 " "
    1451 " "
    1309 " "
    1057 " "

    Info from http://www.reloadammo.com/footpound2.htm- just plug it in.

  10. #10

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    I am wanting to compare the Foot Pounds of Energy as stated above to the Foot Pounds of the 75 or 77 gr. bullet fired from a 5.56/.223 of any given barrel length. Does anyone have the ft.lb. for the 77 gr. bullet....???

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    Member Float Pilot's Avatar
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    Quote Originally Posted by AGL4now View Post
    I am wanting to compare the Foot Pounds of Energy as stated above to the Foot Pounds of the 75 or 77 gr. bullet fired from a 5.56/.223 of any given barrel length. Does anyone have the ft.lb. for the 77 gr. bullet....???
    Hornady has a listing for the 75 gr BTHP as follows:
    Muzzle Velocity: 2790 fps
    Velocity at 100 yards: 2561 fps
    Velocity at 200 yards: 2344 fps
    Muzzle Energy: 1296 ft/lbs
    Energy at 100 yards: 1092 ft/lbs
    Energy at 200 yards: 915 ft/lbs

    A 77 gr bullet at same velocity would be around 1330 ft/lbs at muzzle

  13. #13

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    Quote Originally Posted by Float Pilot View Post

    Sadly I don't know the B.C. and that should NOT matter at the muzzle. I do NOT even know the volicity.

    I Just want to compare the foot Pounds of the 77 gr. .223 in say a 16" barrel to the above data.

  14. #14

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    [QUOTE=AKBEE;1227588]Hornady has a listing for the 75 gr BTHP as follows:



    A 77 gr bullet at same velocity would be around 1330 ft/lbs at muzzle.

    As compared to:

    A 115 gr. bullet out of a 16" barrel 6.8 SPC @ 1627 ft/lbs at muzzle.

    This is useful info. for me.


    Thank You, everyone & special Thank You to "AKBEE".

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    Member Float Pilot's Avatar
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    A good place to get the listed BC of a bullet is the MIDWAY site...

    From the 6.8mm (.277 caliber bullets)

    85gr TSX = .246 bc
    90gr Sierra HP flat base = .195 BC
    95gr TTSX = .296 BC

    100gr Accubond= .323 bc
    100gr Speer HP = .225 bc
    100gr Hornady SP = .307 bc

    110gr Hornady BTHP= .360 bc
    110gr Sierra Prohunter= . 318bc
    110gr V-Max = .370bc
    110gr Accubond = . 370bc
    110gr TTSX = .377 bc
    110gr Tsx HP = .323 bc

    120gr Hornady SST = .400 bc
    120gr Barnes Banded Solid = .438 bc (too long for slow rifling twists)

    130gr Barnes MRX= .380 bc
    130 Speer Grand Slam = .345 bc
    130 Nosler Bal-Tip = .433 bc
    130gr Sierra Game King = .436 bc
    130gr Hornady SST = .460 bc
    130gr Nosler partition = .416 bc (*worked well on caribou)
    130gr Sierra Pro hunter = .436 bc
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    Member tyrex13's Avatar
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    After owning a 6.8 upper for nearly a year and never shooting it I can tell you that you really need to be a reloader to make best use of the caliber in Alaska as anything other than run of the mill Remington ammo is pretty much non existent. I thought it would be a fun hunting stick, but premium ammo availability locally really turned me off to the caliber.

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    Member AKDoug's Avatar
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    I totally agree. However, pretty much any caliber in an AR that you can hunt with is a handloading venture. The only factory ammunition I would trust in .223 are Barnes and a box of them is more than a box of 30-06. Components are available for the 6.8 and I'm a handloader, so it's no big deal for me. I appreciate Floatpilot's data because it's awful tough to find 110grn 6.8's right now, but 130's are all over the place. Looks like my daughter's rifle will be running those. I have to download 140's in her 7-08 to make her comfortable shooting it. Max loaded 130's in the 6.8 are getting really close to those loads in a handier package for her. She's really excited that she will be assembling the whole rifle from the ground up and loading her own ammo.
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    Member martentrapper's Avatar
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    Quote Originally Posted by tyrex13 View Post
    After owning a 6.8 upper for nearly a year and never shooting it I can tell you that you really need to be a reloader to make best use of the caliber in Alaska as anything other than run of the mill Remington ammo is pretty much non existent. I thought it would be a fun hunting stick, but premium ammo availability locally really turned me off to the caliber.
    Your right about the handloading part. Need to hand load to get the best out of the caliber. However, if you travel down south sometimes, or have friends/relatives that do, you can buy ammo at a discount and have them bring it up for you. Silver State Armory specializes in 6.8. Cabelas, Midway, and a dozen other small ammo dealers on the internet sell quality 6.8 ammo at a reasonable price.
    Order a bunch and ship it to ma and pa, your bro, sis, whoever, in the lower 48. Have whoever you know and trust bring it up in luggage. Or get it when you go down.
    I know a couple guys who rotate in to Alaska for work every 2 weeks. I have used them at times to bring up 6.8 ammo. I got 5 boxes of the 140 gr Berger VLDs that way.

    Doug and Lujon got it figured out........and I'm working along a similar path with my kid. A 7mm-08 is alright in a bolt action for a kid. Imagine how much more involved the kid could get building the gun, loading the ammo, sighting it in, shooting it, and hunting with it. Plus........slap a 5.56 upper on the kids gun and practice is CHEAP and FUN!

    Doug, is that New Frontier lower available? PM me.
    I can't help being a lazy, dumb, weekend warrior.......I have a JOB!
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  19. #19
    Member Float Pilot's Avatar
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    [B]6.8mm SPC
    16 and 24 inch barrel velocity and accuracy test.[/
    B]

    16 inch barrel, Stag factory 1 in 10 twist SPC-II chamber
    24 inch barrel, Black Hole Weaponry, 1 in 11 twist, SPEC II.
    Fired at @ 50 degrees F. Alt 350 feet.


    90 grain Sierra JHP
    28.8 grains H-4198
    SSA Brass, CCI-BR-4 primer
    COL- 2.200 inch, Lee Crimp
    16 inch = 2,908 fps and 0.40 inch group
    24 inch = 3,110 fps and 0.75 inch group


    100 grain Bulk mystery SP.
    29.7 grains H-Benchmark
    SSA Brass, Fed 205 primer
    COL=2.255 inch, Lee Crimp
    16 inch = 2,650 fps … Large group
    24 inch = 2,750 fps--- 0.50 inch group, no flyers.

    100 grain Remington SP
    31.5 grains AA-2230
    SSA brass, CCI-400
    COL-2.225”, Lee Crimp
    16 inch = 2,580 fps Group over 2 inches
    24 inch = 2,765 fps… 0.75 inch group

    110 grain Nosler Accubond
    29.0 grains H-322
    SSA Brass, CCI-BR-4
    COL-2.265” Lee Crimp
    16 inch = 2,554 fps and 1.0 inch group
    24 inch = 2,730 fps and one ragged hole at 100 yards.

    110 grain Nosler Accubond
    25.8 grains AA-1680
    SSA Brass, BR-4 primer
    COL-2.250”, Lee Crimp
    16 inch = 2,500 fps and 1.5 in group
    24 inch = 2,770 fps and 0.50 inch group average






    110 grain Sierra Pro-Hunter
    25.8 grains AA-1680
    SSA Brass, BR-4 primer
    COL-2.250”, Lee Crimp
    16 inch = 2,470 fps and 2.5 in group
    24 inch = 2,608 fps and 1.0 inch group average

    110 grain Sierra Pro-Hunter SP
    30.8 grains AA-2230
    SSA Brass, CCI-400
    COL 2,255”, Lee Crimp
    16 inch = 2,550 fps,,1.0 inch group
    24 inch = 2,730 fps ..0.75 inch group


    110 grain Hornady JHP.
    30.8 grains, AA-2230
    SSA brass, CCI-400
    COL=2.255, Lee crimp.
    16 inch = 2,530 fps….. 2.5 inch group
    24 inch = 2,760 fps----1.1 inch group

    110 grain Barnes Triple Shock
    30.5 grains AA-2230
    SSA Brass, CCI-400 primer,
    COL-2.237, Lee Crimp
    16 inch = 2,550 fps 1.5 inch group
    24 inch = 2,820 fps 0.80 inch group

    110 grain Hornady Factory Ammo.
    110 grain BTHP
    16 inch = 2,455 fps
    24 inch = 2,699 fps 1.5 inch group
    110 grain Ballistic tip type load
    16 inch = 2,506 fps
    24 inch = 2,790 fps 1.0 inch group

    130 grain Sierra S.P flat base
    27.0 grains H-Benchmark
    SSA brass, Rem 7.5 primer
    COL= 2.55 inch, Lee crimp
    16 inch = 2,220 fps…1.0 inch group
    24 inch = 2,480 fps and 1.0 inch group
    No pressure signs.
    Floatplane,Tailwheel and Firearms Instructor- Dragonfly Aero
    Experimental Hand-Loader, NRA Life Member
    http://site.dragonflyaero.com

  20. #20
    Member AKDoug's Avatar
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    Thanks for that additional data.

    Doug, is that New Frontier lower available? PM me.
    Checking with him again.
    Bunny Boots and Bearcats: Utility Sled Mayhem

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