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  1. #1

    .300 Blackout and Buffer Weight

    Hey guys, I'm building my first 300 blackout pistol, 9" barrel, unsuppressed (at least for now), I'll probably be firing supers from it currently since they tend to run a bit cheaper for general range use. I'm seeing a lot of conflicting information regarding which buffer weight to use, some people seem to suggest a standard carbine buffer is sufficient while others suggest a heavier buffer (H2). Can anyone provide any personal input? I guess I'm not really sure I understand what the purpose of having the heavier buffer vs. a standard one would be.

  2. #2
    MGO Member SpartyME's Avatar
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    H2 will prevent bolt bounce with supers or suppressed subs.
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  3. #3
    Generally speaking, an h2 buffer would probably suit you better. That said, there is no easy answer. Many things come into play here like gas port size, recoil spring, resistance to re-cock hammer, bcg mass, etc.

    So, really it depends on what all you use. If using "standard" parts, h2 is generally the correct weight.
    Last edited by Cocowheats; 04-04-2018 at 05:08 AM.

  4. #4
    In Memoriam postban's Avatar
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    I just run a a standard carbine buffer in this 8" pistol. Works fine with subs/supers suppressed or not.
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  5. #5
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    Contact the barrel manf and see what they recommend. Make sure to give all relevant info info about the components you are using.

  6. #6
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    Quote Originally Posted by castrotikon View Post
    Hey guys, I'm building my first 300 blackout pistol, 9" barrel, unsuppressed (at least for now), I'll probably be firing supers from it currently since they tend to run a bit cheaper for general range use. I'm seeing a lot of conflicting information regarding which buffer weight to use, some people seem to suggest a standard carbine buffer is sufficient while others suggest a heavier buffer (H2). Can anyone provide any personal input? I guess I'm not really sure I understand what the purpose of having the heavier buffer vs. a standard one would be.

    That is almost impossible to answer without firing the gun with the buffer spring that you have in in the gun, with the bolt carrier that you have in the gun, with the ammo that you intend to use.

    The .300 BlackOut is fun round to play with but can take some tuning to get them to shoot a (weak) subsonic round with proper ejection then turn around & get a hotdog supersonic to not over-gas & slam the bolt back with jaw jarring force.

    Just no way to tell you from afar what the best buffer weight will be when the gun is finally broken in & shooting the rounds that you intend to shoot.

    A LOT depends on the barrel gas hole size (Most short .300 BlackOut barrels come with the gas holes drilled too large as that way they will shoot anything without complaints). But this leaves most over-gassed for most general usage (especially suppressed).

    I usually build the short barrel 300 Blk with a carbine buffer to begin with (this is the best chance of the gun functioning reliably to allow further tuning).

    Once you get the gun shooting with reliability & somewhat broken in then you can then start playing with buffer weights, buffer spring tension, load's work up, etc.

    With the short barrels on the pistol builds, those will have a pistol gas port position, so as a rule they will be over gassed & harsh when shooting most factory supersonics. (but they will usually function with about anything that you toss in the chamber)

    Buffer springs can also vary enough in load & rate to have an effect on tuning so that also has to be part of the tuning equation. (I have a homemade spring tester to compare buffer springs so I can tune with like springs)

    So, my suggestion is to initially build the gun with a carbine buffer just to get it shooting & broken in, then once you get it broken in you can watch the brass ejection pattern, feel the recoil harshness, then play with heavier buffers or weaker/stronger buffer springs until you get a proper ejection pattern with a somewhat soft shooting gun. (pistol gassed .300 BO will never be super smooth)

    If you don't intend to hand-load for the .300 BlackOut then you are at the mercy of the factory loadings & those can vary quite a bit from brand to brand, or in bullet weight, so don't just tune for one brand/weight unless you intend to only shoot that.

    If you shoot only factory supers then you might very well get an H-2 to work (this will take some of the harshness out) but an H-2 probably won't get you bolt lock back with some of the lighter/weaker subsonics. (remember the factory subs will be a fair amount slower out of a short barrel AR)

    The carbine buffer is usually a good (general) buffer if you want reliability with most ammo, full reliability function when dirty, or with weak ammo.

    There is also the H buffer option (3.8 oz) that falls in between the H-2 & the carbine & that can allow a slightly softer super gun but still allow some of the weaker subs to properly cycle unsuppressed.

    Bottom line= build a full functioning gun, THEN, play with tuning to get it to shoot your ammo of choice reliably & as soft as possible.

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