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Thread: Sig’s M4A1 and M249 replacements in 6.8x51

  1. #11
    Site Supporter OlongJohnson's Avatar
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    I predict feeding problems with that steep shoulder angle. A few other thoughts, but they all land in the "this is my surprised face" pile with regard to Sig's proven ability to launch products that are GTG.
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  2. #12
    Quote Originally Posted by jbrimlow View Post
    Is this Gen. Miley's pet project, or does this have some serious support?

    Or, I guess more generally, is there any actual evidence this is going anywhere, unlike the last several times Big Army has tried to replace the M16/M4?
    They are trying to fund this program.

    https://www.military.com/daily-news/...uto-rifle.html

  3. #13
    Interesting that the US Army's desire for a universal platform started 70 years ago is still being sought.

    Rene Studler is generally considered to be the Boogeyman in all this with his desire to stick to 30-06 performance. A lightweight rifle and a full power 30 caliber cartridge are apparently not completely compatible.

    I wonder how SIG's .270 cartridge will perform in this regard. The wonder cartridge has finally arrived or something unpleasant and uncontrollable in an assault rifle?

    Sent from my SM-G930P using Tapatalk

  4. #14
    The 6.8 is supposedly a 135gr lead free EPR.

    Looking at Cutting Edge's copper solid 130gr 6.8, they list a G1 BC of .54, which should be a pretty good placeholder until we know the exact projectile.



    https://cuttingedgebullets.com/277-1...ctical-hunting

    135gr 0.54 G1 @ 3,000fps

    https://bergerbullets.com/ballistics-calculator/

    600m = 1,936fps / 1,123 ftlbs

    760m = 1700fps EPR Frag range

    1290m = 1125fps / 381 ftlbs supersonic range

    It's too much for a standard issue carbine, but should be a hell of a LMG/GPMG round.

  5. #15
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    Quote Originally Posted by spyderco monkey View Post

    It's too much for a standard issue carbine, but should be a hell of a LMG/GPMG round.
    That certainly does seem to be the position of educated people in a position to know. Is the juice worth the squeeze over a 6.5 Creed GPMG?
    Per the PF Code of Conduct, I have a commercial interest in the StreakTM product as sold by Ammo, Inc.

  6. #16
    Quote Originally Posted by Bergeron View Post
    That certainly does seem to be the position of educated people in a position to know. Is the juice worth the squeeze over a 6.5 Creed GPMG?
    Well, there's a number of questions we don't know - how will these guns hold up to the higher pressures (75-85kpsi) of the 6.8 cartridge, how will that effect barrel life, controllability, blast, etc.

    And of course the biggest variable - will the 6.8 ADVAP actually be able to penetrate modern Tile Array Level IV armor at range - given that this armor is now capable of stopping 7.62 M993 Tungsten from 40' away:
    https://www.youtube.com/watch?v=yH8Sls4hxoo

    Now from a pure ballistics standpoint though, the 6.8 does beat 6.5 Creedmoor, similar to how 6.5 beats 7.62:

    7.62 M80
    147gr 0.420 G1 @ 2750fps
    490m = 1700fps
    600m = 1510fps / 745 ftlbs
    900m = 1125fps / 415 ftlbs supersonic range

    6.5 Creedmoor
    125gr 6.5 EPR 0.55 G1 @ 2750fps
    600m = 1761fps / 861 ftlbs
    640m = 1700fps EPR Frag range
    1180m = 1125ps / 354 ftlbs supersonic range

    6.8 HVAP
    135gr 6.8 EPR 0.54 G1 @ 3,000fps
    600m = 1936fps / 1,123ftlbs
    760m = 1700fps EPR frag range
    1290m = 1125 fps / 381 ftlbs supersonic range
    Last edited by spyderco monkey; 05-27-2019 at 06:15 PM.

  7. #17
    Site Supporter DocGKR's Avatar
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    While a tougher threat than 1940's era .30-06 M2 AP, the mid-1990's adopted M993 is no longer state of the art, nor is LIV armor....
    Facts matter...Feelings Can Lie

  8. #18
    Quote Originally Posted by DocGKR View Post
    While a tougher threat than 1940's era .30-06 M2 AP, the mid-1990's adopted M993 is no longer state of the art, nor is LIV armor....
    Yes, there are more advanced projectiles out there.

    That said, if we have commercial off the shelf Level IV capable of stopping 130gr M993 @ 2860fps + 152gr Tungsten @ 2820fps from 40' away, it seems suspect that a 135gr 6.8 is going to be defeating armor at 300m+ as initially advertised.

    Personally I think the focus on AP is a fools errand:
    -The enemies we are currently fighting, and ones we are actually likely to fight in the coming decades, don't wear any sort of body armor.
    -Russia and China are capable of building similar plates to the RMA now, which will likely greatly reduce the AP penetration range of 6.8
    - The very fielding of 6.8 will spur further innovation in the field of armor to counter this threat, likely being able to stop the 6.8 within the decade or less.

    -->We're fielding a needlessly powerful battle rifle to counter a non-existent armor threat that will no longer be AP within the decade.

  9. #19
    Site Supporter DocGKR's Avatar
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    I rarely believe any hype coming out of big Army.

    Concur regarding armor escalation--one can always improve armor when facing a new projectile; there is already armor available which can stop .300 WM, .338 Mag, and even .50 BMG, so stopping the new 6.8 is not going to be too hard if one really want to.
    Facts matter...Feelings Can Lie

  10. #20
    So will the new 6.8 round require a large frame AR?

    Also found this interesting article.

    https://www.militarytimes.com/news/y...-lot-deadlier/

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