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Thread: What weight buffer?

  1. #1
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    What weight buffer?

    Is there a need to run the "H" buffer with the mid-length or is standard buffer good to go since the mid-length gas system is not as harsh as the carbine gas system?

    I have a middy with an "H" buffer and haven't had any issues; however, I primarily use XM193 and SA ammo. I don't know if lower powered loads would cause issues.

    Any feedback will be appreciated.

    edited title and made a sticky since this topic/question comes up about twice a week.--gotm4
    Last edited by Robb Jensen; 12-08-08 at 05:23. Reason: making a sticky since the question is asked often

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    i run H in all my middies. i'm running CARs in my 7"s until my ISMI springs wear in a bit. too stiff for the H buffer right now it seems.
    Last edited by Parabellum9x19mm; 12-08-08 at 00:11.
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    The midlength gas system being longer lowers the amount of gas pressure at the gas port thus heavier buffers aren't required. CAR would work fine, H will work but with weaker ammo or a dirtier gun it will likely jam (short stroke, running to slowing to feel as good as a faster cycling gun).

    H, H2, H3 and buffers were designed for CAR and shorter gas systems. Do they sometimes work with longer than CAR gas systems? Of course.

    Think about the design of the AR15, it was designed as a rifle. It had a 5.2oz rifle length buffer and a reduced power buffer spring. Then along came the CAR length rifles XM177 it with short barrels because the gas port was much closer to the muzzle the gas port needed to be make larger. The larger gas port and shorter gas tube sends more gas volume and higher pressure through the gas tube, this results is higher bolt velocity and more wear on parts etc.
    To ensure that the shorter gun has enough has volume and enough time to completely cycle the gas ports were left large, but to slow the violent bolt velocity heavier buffers were designed.

    CAR buffers springs are shorter and stiffer than rifle length buffer springs.

    CAR buffers = 3.0oz
    H buffers = 3.8oz
    H2 buffers = 4.6oz
    H3 buffers = 5.5oz
    Rifle buffers = 5.2oz

    Gas port (that hole in the barrel) pressures:
    Rifle = 13.5K
    Midlength = 19K
    CAR = 26K

    Be care running heavier buffers is some barrels like BCM, LMT, Colt and some others which run mil-spec sized gas ports designed for 5.56mm NATO pressure ammo. I've seen many people use a LMT 16" gun and a H2/H3 buffers and/or a LMT enhanced bolt carrier and Crane O-rings on the extractors and then only ever shoot .223 Rem pressure ammo (because it's cheaper) thinking their being wiser then the next guy and then wonder why their rifle keeps short stroking or failing to feed. Sometimes a little bit knowledge is dangerous.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

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    Quote Originally Posted by gotm4 View Post
    Sometimes a little bit knowledge is dangerous.
    VERY true! It's important to understand the "why" of a thing as well as the "how".

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    Quote Originally Posted by gotm4 View Post

    Be care running heavier buffers is some barrels like BCM, LMT, Colt and some others which run mil-spec sized gas ports designed for 5.56mm NATO pressure ammo.
    Good to know, since my next build will be sporting a BCM mid-length upper. My other rifle, and first mid-length build, is sporting a GTS Operator upper and running an H buffer. And, I take it that this barrel (Mike Rock) probably doesn't sport a mil-spec gas port?

    ETA: And leave it up to me to post the millionth question about buffers that causes the mods to get tired of it and make it a sticky. Lol.
    Last edited by urbankaos04; 12-08-08 at 21:47.

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    i'm running H buffers in BCM and Noveske middies and 5.56 ammo with no ill effects. then again i haven't let those uppers get supper cruddy yet. i always add lube before i shoot, so they haven't gotten sluggish on me yet.
    Last edited by Parabellum9x19mm; 12-09-08 at 04:28.
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    So I shouldn't put an H buffer in my LMT lower that I plan to put an LMT or BCM upper on? Should I put them in my RRA lowers that I'm running Stag uppers with Larue BCGs on?

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    rob_s and gotM4 are recommending the CAR buffer for the middy and H for the CAR gas system. this appears to be SOP for many users here. it makes sense too, the heavier buffer for the higher pressure system.


    rob_s and gotM4 know a lot more about firearms and shooting than i do. i'd listen to them before you heed any bullshit i say.


    you can always experiment with your firearms and ammo and see what works best for you. either it will start short stroking eventually or it wont. the type of buffer spring you are using will also effect this, as i have found out.
    Last edited by Parabellum9x19mm; 12-09-08 at 06:21.
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    FWIW

    The Canadian Army went with an H2 buffer for its C7A2 rifles -- which is basically a 20" flattop upper with a M4 stocked lower. They found the H2 gave the best performance with NATO ammo over the range of bbl lengths (10" to 20" , as some units get mutliple uppers).

    I've run H2 buffers on all my middies, my SR16 16"middy upper I used in Afghan and Iraq was used both suppressed and unsuppressed with ammo's from M193, M855, M856 and Mk262 as well as AA40 Frang.

    The H2 is my 'go to' buffer weight, and I would deviate from it on a gun only if I have problems.

    Granted 99.9% of the time I am shooting Mil-Spec ammo.
    Kevin S. Boland
    Manager, Federal Sales
    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
    www.fnhusa.com

  10. #10
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    yeah, I generally shoot PMC or S&B .223, I do have some mil-spec 55 gr and 62 gr, but that's pretty much being saved for when the SHTF. I'll put the H buffers in my RRA lowers and I'll leave the LMT lower alone for now

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