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Thread: M855A1 with H6 buffer?

  1. #71
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    Dopey Me missed the fact there was two more pages to the American Rifleman article. Still, it does not answer the question as to what method was used to measure pressure. If the NATO method was used, M855 ammo at 53k is well under the NATO spec which, if I recall correctly, is 62k. If M855A1 is 3-5k greater, that's only up to 58k, still less than NATO max. If measured using the SAAMI method, 58k is at the high end but still nowhere near proof load pressures as some claim. The 300 WSM had it's pressure set just over 60k SAAMI when it was introduced.

    This sheds a bit different light on over-gassing and the real difference between SAAMI spec 223 ammo and NATO spec 5.56
    Last edited by MistWolf; 05-29-14 at 14:57.
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  2. #72
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    Quote Originally Posted by MistWolf View Post
    Still, it does not answer the question as to what method was used to measure pressure.
    Regardless of method, It's still an increase of somewhere around 3k on a round that's already rough on the mil M4.
    "You people have too much time on your hands." - scottryan

  3. #73
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    Yes, I realize that. That' why I said it sheds a different light on over-gassing & the differences between 223 & 5.56.

    It also begs the question- How does M855 and M855A1 pressures compare to other NATO spec ammo? Is it less? Is it the same? What other NATO spec ammo is considered hard on the rifle? This information raises as many questions as it answers
    Last edited by MistWolf; 05-29-14 at 15:24.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

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  4. #74
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    Quote Originally Posted by MistWolf View Post
    Yes, I realize that. That' why I said it sheds a different light on over-gassing & the differences between 223 & 5.56.

    It also begs the question- How does M855 and M855A1 pressures compare to other NATO spec ammo? Is it less? Is it the same? What other NATO spec ammo is considered hard on the rifle? This information raises as many questions as it answers
    Well here are the mil specs for chamber pressure for M855 on TOS.

    http://www.ar15.com/content/page.html?id=434

    NATO uses CIP figures to articulate chamber pressure, but the army seems to use a nearly SAAMI equivalent method for their measurements.

    I'll bet that to increase muzzle velocity at or above 3100 fps from just above 2950 fps for the M4's 14.5" barrel, a nearly 10% increase in chamber pressure seems to make sense.

    We're talking exceeding M193 velocity with a bullet that is nearly as long as a 69 gr SMK/62 gr TSX.

    Something has to give. Regardless of the exact figure for A1 chamber pressure, it's wildly excessive. Period.

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  5. #75
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    Quote Originally Posted by BufordTJustice View Post
    W
    Regardless of the exact figure for A1 chamber pressure, it's wildly excessive. Period.
    When you have to switch from a crimp to 4 aggressive stakes to keep the primers from popping.... that's a CLUE.

    I don't care how temp stabile they claim the propellant is. When you're in a hot climate and the gun is over 110 degrees before even firing a shot?? I'd be praying for the gun to hold together, that's for sure.
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  6. #76
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    Quote Originally Posted by U.S.Cavalryman View Post
    I was there too. All the way in the back, in the GravelCam Army section. This comes from multiple sources.
    I wish we would have hooked up...at least for a beer afterwards.

    I was the civilian that asked if they realized the Navy wouldn't allow them to paint their rifles on ship. I also questioned them on the robot moving targets......that test was rigged.

  7. #77
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    Quote Originally Posted by BufordTJustice View Post
    Well here are the mil specs for chamber pressure for M855 on TOS.

    http://www.ar15.com/content/page.html?id=434

    NATO uses CIP figures to articulate chamber pressure, but the army seems to use a nearly SAAMI equivalent method for their measurements.

    I'll bet that to increase muzzle velocity at or above 3100 fps from just above 2950 fps for the M4's 14.5" barrel, a nearly 10% increase in chamber pressure seems to make sense.

    We're talking exceeding M193 velocity with a bullet that is nearly as long as a 69 gr SMK/62 gr TSX.

    Something has to give. Regardless of the exact figure for A1 chamber pressure, it's wildly excessive. Period.

    Sent from my SPH-L720T using Tapatalk
    But it is also not nearly proof loads as some claim.
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    This is 2012. The world is going to end this December and people are still trying to debate the merits of piece of shit, cost cutting crap AR's. Really?

  8. #78
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    Boland says he saw 62Kpsi to 65Kpsi back in 2011.

    And 72Kpsi in a 249.

    He also says in the same thread that C. Reed Knight was quite alarmed by the pressure signs from the ammo when he evaluated it.

    http://www.lightfighter.net/topic/m8...cations-anyone

    It seems my statement about it nearly being a proof load remains accurate unless Kevin has since learned additional info.

    Take a round that has been chambered a few times with some heat and maybe a little lube. .... KABLOOEY.

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    Last edited by BufordTJustice; 05-29-14 at 19:34.
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  9. #79
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    Quote Originally Posted by sinlessorrow View Post
    But it is also not nearly proof loads as some claim.
    A proof load is just over 70kpsi and is designed to be fired ONCE. Coming within 6kpsi or 7kpsi of that for EVERY ROUND FIRED THROUGH A GUN is absurd.

    The difference between A1 and 855 is almost double the difference between max SAAMI spec .223 and 5.56 NATO.

    I highly doubt the army would mince words with regard to chamber pressure that would exaggerate the increase. ... An increase which they refused to PRINT in initial documents.

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  10. #80
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    GTF425, Thanks for your service! If you got your M4A1's problems all figured out I'm glad. If not and you still need a H2 buffer or whichever buffer for that matter and/or the correct springs, I'd be more then happy to buy them for you. I'd just have to figure out how to get them to Afghanistan. But I'll do it!

    Let me know, NYH1.
    Last edited by NYH1; 05-30-14 at 03:09.

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