Page 1 of 2 1 2 LastLast
Results 1 to 10 of 14

Thread: 6.8SPC Conversion Thoughts

  1. #1
    Happy Camper hcpookie's Avatar
    Join Date
    Feb 2004
    Location
    Colorado Springs
    Posts
    7,691
    Feedback Score
    3 (100%)

    Default 6.8SPC Conversion Thoughts

    I know this has been asked in the past, but no numbers were ever collated.

    Why the 6.8 SPC? Two main reasons - it performs close to the .308 out to 400 yards, and does this in a smaller bullet (.277 aka 270 caliber) and a smaller cartridge that fits in an AR magazine. It fills that gap of needing .308 performance at "normal" ranges but in a smaller, lighter package.


    The cartridge parent case is the (obsolete) .30 Remington that has been shortened to fit inside an AR15 magazine. New and once-fired brass is available for those like me who reload... making this a more economically lucrative prospect. Reloading supplies are easily obtained for this round... standard .270 bullets are used. Barrels are readily available from the major sources.


    The limitations to this cartridge are the size of the base, which is approximately .418" diameter. That's based off of the 6.8 cases I have in my brass collection, not off of a website. The only bolt that is close enough for this to work as a conversion would be the .223 bolt face. The 7.62x39 and .308 bolt faces are simply too large. I do not know what are the chamber pressures for the 5.45x39, so I am hesitant to list that as an available platform for conversion. I do not know if the metal is of a different grade than the .223 AK bolts, however visually they are nearly identical in all dimensions. I for one would stay focused on the .223 platform since that is readily available in today's market. If I can find some chamber pressure info for the 5.45, this may make it onto the list. The .223 bolt face could be opened up larger on a lathe as well as the extractor and you would have your 6.8 bolt!


    Since this cartridge was tailored to fit inside an AR magazine, it goes without saying that a .223 magazine would be the ideal base magazine. As some of you may already know, I have been converted an AR follower to work in a .223 AK magazine, so I know this magazine conversion is doable, even if special followers are required.


    Most importantly, the chamber pressures as listed on the Hodgdon Powder website place this right at the 50,000 PSI mark, making this an acceptable cartridge for use in a .223 action such as a Saiga .223 or Galil.


    The default bullet sizes seem to be standardized on 115 grain, but different grain loads are available.


    Generally speaking, the "smaller, shorter magnum" concept that spawned this cartridge seems to be a natural fit for conversion to an AK platform.


    A few references:

    The 6.8 SPC Directory - 6.8mm Remington SPC Ammo, Bullets, Rifles

    Cartridge Loads - Hodgdon Reloading Data Center - data.hodgdon.com

    6.8SPC
    *dead link, archive here: Internet Archive Wayback Machine

    6.8SPC FAQ






    Now, do I use my Galil parts kit to make a 6.8, or... ?
    Last edited by hcpookie; 05-10-2010 at 02:47 PM.
    Gunco Member #10

    http://pookieweb.net


    The "original" Boltcutter Rivet Squeezers:
    http://pookieweb.net/AK/rivet/boltcutters/boltcutter.htm


    Project Pink - the Pink and Blue AK-74:
    http://pookieweb.net/pink/pink.htm

  2. #2
    No Hope For Me 1biggun's Avatar
    Join Date
    Oct 2005
    Posts
    13,586
    Feedback Score
    14 (100%)

    Default

    I have had a 6.8 SPC stainless heavy varmit barrel (remington take off) for over 2 years and a 223 Bulgy bolt to enlarge for a 6.8 SPC build. time and other projects have been infront of it. I posted here and on another site several times abought it.


    A AR to AK mag adapter was the original plan but those all got bought up and now are really pricey.

    I have put 4 rounds of 6.8 into a unknown steel 5 round 223 mag and they seem fine to me. they dont fit well in my bulgy plastig mags as well the lips are just a little to far apart to hold them in they jump out easly. Now here is some thing interesting. In the only 223 ProMag I own I can easly get a whole box of twenty rounds in to the 30 round mag and they seem to not bind or jump out This may be a doable cheap USA mag for this build (I am very aware of Pro mags poor reputation and this mag works poorly in my 223)



    my plan was to use a Rommy kit and add the bulgy bolt just like my 223 varmit build. however I can say that a 7.62x39 bolt will pull a 6.8 round round out of a normal AK I just put a round in the barrel (it wont fit all the way in ) and closed the bolt by hand and it will catch and pull and eject it with no mods!!! HMMMMM I cant say what it will do with a fired and expanded case fully seated in the correct chamber however, IT IS POSSABLE THAT A 7.62X39 BOLT WILL WORK AS IS OR MAYBE WITH A MODIFED EXTRACTOR POSSABLY A TRIMMED 223 OR 5.45 ONE. I get a .418 rim on my silver state armory brass and I have seen 7.62x39 brass as small as .440 so were only talking
    .022 differance here. If a 7.62 bolt will work this will make this a lot easyer and cheaper build IF IF IF.

    also any 270 winchester barrel could be rechamberd to this round for a dirt cheap build

    to be honest I dont see the 6.8 nearly as good as a 308 the trajectory is close only when you compare the 115 GR 6.8 to a 150 GR 308. and even then at 300 meters the the 308 is faster an has 200lbs more energy. at 100 meters the 308 has a lot more energy almost 500lbs thats a lot IMOA.

    were the 6.8 rally shines is over the 5.56 77 gr were it has very simular velocitys clear out to 1000 meters but at that range has nearly twice the energy (228 LBS )

    dont get me wrong the 6.8 spc is a lot better than a 223/5.56 but is to far from the 308 IMOA to be in the same class. also if a lighter 308 bullet were compared the 308 really out shines the 6.8 with a lot more speed.



    As far as on A AK platform pressures are no issue as the reduced rim size equates to 7.62x39 bolt thrust pressures. as far as the 5.45 pressures giving the velocity these shoot I, suspect it is right at 50,000 PSI as well. This is a build I am going to do at some point. likely in a hunting pistol. I really would rather have a 6.5 Grendal or a 243,260 remington, 250 savage ,300 savage, or a 308 even loaded to a lower pressure over the 6.8 SPC IMOA


  3. #3
    BANNED nalioth's Avatar
    Join Date
    Feb 2006
    Location
    Houston, Texas
    Posts
    1,529
    Feedback Score
    4 (100%)

    Default

    Here's another thought (some of you might not have heard of it)


    The 6.5 MPC ( multi purpose cartridge ).

    This is a .223 case necked up for a 6.5mm bullet.

    Only change needed to run it in existing 5.56mm weapons is a new barrel.


    Four different bullets in the 6.5 MPC. Note all are
    seated to 5.56 OAL to run through M-16 magazines.

    Image courtesy of SSK Industries

    Quote Originally Posted by Defense Review
    SSK 6.5 MPC: Best Assault Rifle Cartridge for 21st Century Warfare?
    Posted on Sunday, December 31 @ 11:54:47 PST by davidc

    Ammunition by David Crane
    david at defensereview.com

    Small arms designer/developer J.D. Jones of SSK Industries has developed what may just prove to be a superior solution to the 6.8x43mm SPC (a.k.a. 6.8 SPC) and/or 6.5 Grendel (6.5x39mm) cartidges as a replacement for the 5.56x45mm NATO cartridge for U.S. military general infantry and Special Operations (USSOCOM) use. Mr. Jones is calling it the 6.5mm Multi-Purpose Cartridge (6.5 MPC), and on paper, it looks pretty good.

    The 6.5 MPC (6.5x42mm) utilizes the...


    standard 5.56x45mm NATO/.223 Rem. case, which must be shortened by three (3) millimeters. However, to maximize powder capacity (and thus projectile velocity and ballistic/terminal performance), Mr. Jones pushed the case shoulder back a tad and increased the size of the case neck so it would accept a 6.5mm bullet. The result? A 95-grain "SSK Solid" bullet travelling at a muzzle velocity (MV) of approx. 2600 fps out of a 12-inch (12") barrel and approx. 2800 fps out of a 20-inch (20") barrel. So, were' guessing around 2700 fps out of a 16-inch (16") barrel (unconfirmed/unverified). Pretty respectable. Muzzle velocities for the 110-grain Sierra HP version of the 6.5 SPC are 2480 fps (12") and 2731 fps (20"). MVs for the 120-grain "SMK" round are 2220 fps (12") and 2400 fps (20"). 120-grains is the upper limit of bullet weight for this cartridge. Anything above that affords limited ballistic returns. Impact energy (terminal energy) is reportedly 30-50% greater for the 6.5 MPC over the 5.56mm NATO, depending on bullet weights and types, while the weapon remains highly controlloble on full-auto.

    The 6.5 MPC page at the SSK Industries website mentions that they've fired a 107-grain SMK round at 2400 fps out of a weapon with a 12"-barreled CQBR-type upper receiver and that effective engagement range is 300+ yards. With longer barrels, the distance is increased.

    So, why the 6.5 MPC instead of the 6.8 SPC? Ease and cost of conversion (weapons conversion), ammo capacity, and ammo weight (ammo carry capacity at a given load weight). The 6.5 MPC utilizes standard AR-15/M16/M4/M4A1 magazines and bolts, and will function in both the SOPMOD M4/M4A1 Carbine and belt-fed FN M249 SAW/LMG, provided you switch out the barrel(s). No further modification is reportedly necessary. Mag capacity for the 6.5mm MPC is 30 rounds (although you might still want to down-load it to 28, as many do with 5.56mm ammo for reliability purposes). The 6.8mm SPC doesn't stack properly in standard 5.56mm M4/M4A1 mags, and the magazines that have been developed for it limit ammo capacity to 25 rounds, as opposed to 30 rounds, so the 6.8 SPC mags will fit inside current military mag carry pouches. You can also use 5.56 NATO stripper clips to load 6.5 MPC rounds into the mag. At present, there are no 6.8 SPC stripper clips.

    6.5 MPC ammo will reportedly feed as reliably as 5.56x45mm NATO ball ammo, and it (6.5 MPC) can utilize standard M27 links (belt links) with no modification, so it will reportedly feed reliably through the M249 SAW. You only have to switch the barrel to 6.5mm caliber. Not so with the 6.8 SPC, which would require modification to the M27 link.

    The 6.8 SPC cartridge weighs approx. 40% more than the 5.56mm NATO cartridge. That, combined with the fact that 6.8 SPC mags are made of steel instead of aluminum (making the magazine roughly twice as heavy), means that the infantry warfighter or Spec-Operator will be able to carry less rounds of 6.8 SPC vs. 6.5 MPC or 5.56 NATO.

    Reported ammo carry capacity breakdown for the various cartridges at the same carry weight (specific weight unkown, and unconfirmed/unverified):

    5.56 NATO: 10 x 30-round mags = 300 rounds

    6.5 MPC: 9 x 30-round mags = 270 rounds

    6.8 SPC: 7 x 25-round mags = 175 rounds

    DefenseReview recommends that you read Stan Crist's article on the 6.5mm Multi-Purpose Cartridge in the #44 issue of Special Weapons for Military & Police (SWMP) magazine. That issue has a photo of a U.S. Ordnance M60E4/MK43 Mod1 Commando "light machine gun series" GPMG (7.62x51mm) on the cover, and the article is titled "SSK 6.5mm MPC: Multi-Purpose Cartridge delivers bet-your-life performance." While SSK Industries Website indicates that they developed the 6.5 MPC round at the behest of one Brian Hormberg (USMC), it should perhaps be noted that Stanley Crist mentions in his article that he wrote about his own idea for a 6.5mm assault rifle cartidge in the #36 Issue of Special Weapons for Military and Police. Mr. Crist called his cartridge the 6.5mm Standard Combat Cartridge (6.5 SCC).

    Bottom line, if the 6.5 MPC proves reliable in the AR-15/M16 and SOPMOD M4/M4A1 platforms, is combat accurate out to realistic assault rifle engagement distances, and the AR-type upper receivers and barrels hold up to full-auto fire at high round count, then it may just be the ticket for the 5.56's replacement (and thus a better answer than the 6.8 SPC or 6.5 Grendel) for infantry assault rifles and carbines. Time, money, and politics will tell.
    Original Defense Review article.

    The cartridge inventors page on this new cartridge.

    The great google provides.

  4. #4
    No Hope For Me 1biggun's Avatar
    Join Date
    Oct 2005
    Posts
    13,586
    Feedback Score
    14 (100%)

    Default

    hOLLY CRAP i SAVED THAT SAME LINK JUST THIS MORNING AND JUST POSTED IT IN A NEW THREAD. WOW SMALL WORLD. i WAS LOOKING AT THERE 6.8 sPC OFFERINGS WHEN i FOUND IT.

  5. #5
    Gunco Veteran gunnysmith's Avatar
    Join Date
    Feb 2004
    Location
    Wyo
    Posts
    1,542
    Feedback Score
    6 (100%)

    Default

    From the availability of 5.56 brass, 6.5 MPC would be my choice.
    Constitution Or Bust
    Ron Paul 2012

  6. #6
    No Hope For Me 1biggun's Avatar
    Join Date
    Oct 2005
    Posts
    13,586
    Feedback Score
    14 (100%)

    Default

    there claiming almost the same velocity as the grendal. HMMMM im suspecting they have there running a little more chamber pressure with that smaller case. the bullet they are using is slightly lighter as well. grendal starts with a higher BC bullet that is a 108 GR vs a 95 grain SSK? solid. still seems better than a 223 for combat situations IMOA. Not sure about other uses.

  7. #7
    Happy Camper hcpookie's Avatar
    Join Date
    Feb 2004
    Location
    Colorado Springs
    Posts
    7,691
    Feedback Score
    3 (100%)

    Default

    Quote Originally Posted by gunnysmith View Post
    From the availability of 5.56 brass, 6.5 MPC would be my choice.
    I've been looking around and I can find 6.8 brass with relative ease, even once-fired brass. I even found some at the range last time I went
    Gunco Member #10

    http://pookieweb.net


    The "original" Boltcutter Rivet Squeezers:
    http://pookieweb.net/AK/rivet/boltcutters/boltcutter.htm


    Project Pink - the Pink and Blue AK-74:
    http://pookieweb.net/pink/pink.htm

  8. #8
    No Hope For Me 1biggun's Avatar
    Join Date
    Oct 2005
    Posts
    13,586
    Feedback Score
    14 (100%)

    Default

    it appears that the 6.8 has more case capacity than the 223. this would make a nice .22 wildcat. A 22-SPC might fit in some were between the 223 and the 22-250. HMMMM I would love to get another 200 fps out of my varmit setup. the grendal will neck down as well basicaly a 22 PPC then however

  9. #9
    Gunco Veteran muttman's Avatar
    Join Date
    Dec 2004
    Location
    west, TN.
    Posts
    1,172
    Feedback Score
    0

    Default

    just when I thought it was safe to build a 5.56 now this. I need to stop reading new post. muttman

  10. #10
    Happy Camper hcpookie's Avatar
    Join Date
    Feb 2004
    Location
    Colorado Springs
    Posts
    7,691
    Feedback Score
    3 (100%)

    Default

    I updated the dead links in the first post
    Gunco Member #10

    http://pookieweb.net


    The "original" Boltcutter Rivet Squeezers:
    http://pookieweb.net/AK/rivet/boltcutters/boltcutter.htm


    Project Pink - the Pink and Blue AK-74:
    http://pookieweb.net/pink/pink.htm

Page 1 of 2 1 2 LastLast

Search tags for this page

There are currently no search engine referrals.
Click on a term to search our site for related topics.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •