6.8 spc vs 6.8 spc II
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  1. #1
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    Default 6.8 spc vs 6.8 spc II

    Ok I have searched for any data on loading SPC II. I can find tons of data for the SPC but none for the II. If there is a thread on here I missed it and could somebody point me to it. I loaded some up last night using H335 and with the data from Hodgdon it said start with 27 gr and max is 29.5. Can my SPC II go with a heavier load? My groups started to tighten up at 29.5 grains. Is there something like an SPC II can handle 10% more powder then the SPC? Or is it all work your way up until you see signs then back off type of thing?

  2. #2
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    At the top of the Ammunition/Reloading section

    Bunch of Stickies for different bullets, etc

    Welcome

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    Quote Originally Posted by Warfarin View Post
    Ok I have searched for any data on loading SPC II. I can find tons of data for the SPC but none for the II. If there is a thread on here I missed it and could somebody point me to it. I loaded some up last night using H335 and with the data from Hodgdon it said start with 27 gr and max is 29.5. Can my SPC II go with a heavier load? My groups started to tighten up at 29.5 grains. Is there something like an SPC II can handle 10% more powder then the SPC? Or is it all work your way up until you see signs then back off type of thing?
    This is the only published SPCII load data.
    http://www.accuratepowder.com/wp-con...2016_Web-1.pdf
    Page 42, you will see loads up to 58,500 PSI.

    Hodgdon's data is SPCI, so is everyone elses except for Western Powder.

    As was already stated the stickies have many loads to 60,000 PSI that have been run for years.
    Always start 10% low and work up for your barrel.

    Here is another good guide:
    http://68forums.com/forums/showthrea...hing-to-ponder

    Be safe
    Cavity Back Bullets

    Home of custom precision CNC milled projectiles and more.

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    IronWorks Tactical

    The 6.8 SPCII, the best all around cartridge available in the AR15 platform.

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  5. #4
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    Quote Originally Posted by Yamaraja View Post
    This is the only published SPCII load data.
    http://www.accuratepowder.com/wp-con...2016_Web-1.pdf
    Page 42, you will see loads up to 58,500 PSI.

    Hodgdon's data is SPCI, so is everyone elses except for Western Powder.

    As was already stated the stickies have many loads to 60,000 PSI that have been run for years.
    Always start 10% low and work up for your barrel.

    Here is another good guide:
    http://68forums.com/forums/showthrea...hing-to-ponder

    Be safe
    The Accurate data is for both SPC and SPCII

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    Quote Originally Posted by wxl View Post
    The Accurate data is for both SPC and SPCII
    SAAMI is 55,000 psi.
    They are not saying you can run 58,500 psi in a SPCI SAAMI chamber the way I read it.
    As always when we load our own the drill is to start at the starting load and work up.
    In a SAAMI chamber you will see pressure signs before you would in a SPCII chamber, land groove ratio, forcing cone angle.

    So for instance the 120 SST they rate to 27.2 grains of 2200 at 2.26 OAL.
    We know from years of experience with an SPCII barrel you can run 27.5 at 2.285 or 2.295 OAL. 27.2 is about right for 2.26 OAL
    Now in an SPCI chamber with a .050 freebore, and a 50:50 land groove ratio you will hit pressure sooner.

    In SAAMI spec manuals they do not rate the cartridge to 58,500 PSI but rather hold it to 55,000 PSI.

    Now we can take it a step farther.
    SAAMI rate's the SPCI chamber:
    Maximum Average Pressure(MAP) - 55,000 PSI
    Maximum Probable Lot Mean (MPLM) - 56,400 PSI
    Maximum Probable Sample Mean (MPSM) - 58,500 PSI

    When we load to SPCII like all the data in the stickies or the pressure testing in "something to ponder" it looks more like this. This is what the SAAMI SPCII rating would look like in my opinion.
    Maximum Average Pressure(MAP) - 58,500 PSI
    Maximum Probable Lot Mean (MPLM) - 59,900 PSI
    Maximum Probable Sample Mean (MPSM) - 62,000 PSI

    This to say when loading to 58,500 PSI you could potentially have a deep seated bullet or an overcharge of .2 grains that took a sample from the lot to 59,900 PSI.
    Which my friends at Western Powder and Constructor both say is fine, sometimes hard on brass, likely see some swipes and some flattening primers but not unsafe for the chamber according to them.
    Now at an MPSM of 62,000 PSI you are going to see very distinct pressure signs and case head expansion, ruined brass and cratered primers.

    Now all this is centered around production ammo. The hand-loader can maintain very strict powder charges and good reloading practices and never get to the MPSM level.
    Thus taking advantage of the 58500 to 60,000 psi levels.

    Cavity Back Production ammo will be in the 57,000 PSI to 58,000 PSI range as tested.
    This will leave a good safe margin and take advantage of SPCII.

    All that said, always start low. Work up to your barrel with your components. Don't just run someone else's loads. Use safe reloading practices.
    Last edited by Yamaraja; 05-03-2017 at 01:10 AM.
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    The 6.8 SPCII, the best all around cartridge available in the AR15 platform.

  7. #6
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    Yam,

    Just referencing what is in their manual on page 42

    Quote RIFLE DATA
    6.8 REMINGTON SPC
    These loads apply to both 6.8SPC and SPC II.
    Barrel: 20” ¦ Twist: 1-10” ¦ Primer: WIN WLR ¦ Bullet Diameter: 0.277”
    Case: REM ¦ Max Case Length: 1.686” ¦ Trim Length: 1.676”

    They are indicating all of their loads are safe in SPC


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    Quote Originally Posted by wxl View Post
    Yam,

    Just referencing what is in their manual on page 42


    They are indicating all of their loads are safe in SPC
    Not true.....NO maximum load data from any companys load data is safe in all firearms, got to read those fine print details.. .the only 100% safe firearm is the exact one they tested it in.

    ALL load data manuals say to start at the minimum and work up...so what they are saying is that the minimum powder charges,are safe in both spec1 and spec2, but the maximum charges may NOT be safe in all rifles.

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    Quote Originally Posted by Texas Hog Man View Post
    Not true.....NO maximum load data from any companies load data is safe in all firearms, got to read those fine print details.. .the only 100% safe firearm is the exact one they tested it in.

    ALL load data manuals say to start at the minimum and work up...so what they are saying is that the minimum powder charges,are safe in both spec1 and spec2, but the maximum charges may NOT be safe in all rifles.
    Exactly THM.
    Cavity Back Bullets

    Home of custom precision CNC milled projectiles and more.

    Affiliates:
    AR15 Performance
    IronWorks Tactical

    The 6.8 SPCII, the best all around cartridge available in the AR15 platform.

  10. #9
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    I will defer to the experts, THM & Yam

  11. #10
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    Default

    Great info thanks


 

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