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Thread: M4A1 Barrel 14.5”?

  1. #11
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    I like the BCM A2X extended FH. At a quick glance it's hard to tell that it's longer, and quite frankly a little length to a FH will enhance it's flash hiding abilities. It also comes pre-drilled with a pin. I have several of them.
    11C2P '83-'87
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  2. #12
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    i have two 14.5” M4 barrels with pinned extended A2s. One of them is a BCM M4 barrel that has a BCM A2X that I sent to John Thomas, came out great and the extra length of the flash hider is barely noticeable. The other is a Windham barrel that came with their extended A2 already pinned in place. The Windham A2 is longer than it needs to be and consequently is much more obvious and looks kind of clunky in my opinion

    I also have two 14.7” barrels with pinned standard A2s.
    If retaining the ability to mount a bayonet matters to you, going the 14.7” route or with a spacer+standard A2 will prevent it, whereas you can still do it with an extended flash hider.

  3. #13
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    Quote Originally Posted by Circle_10 View Post
    i have two 14.5” M4 barrels with pinned extended A2s. One of them is a BCM M4 barrel that has a BCM A2X that I sent to John Thomas, came out great and the extra length of the flash hider is barely noticeable. The other is a Windham barrel that came with their extended A2 already pinned in place. The Windham A2 is longer than it needs to be and consequently is much more obvious and looks kind of clunky in my opinion

    I also have two 14.7” barrels with pinned standard A2s.
    If retaining the ability to mount a bayonet matters to you, going the 14.7” route or with a spacer+standard A2 will prevent it, whereas you can still do it with an extended flash hider.
    Question: Does an M4 bayonet normally index on the barrel, or on the FH? I just tried mounting an OKC-3S on the 16" C8, and all was fitting well until it bottomed out against the fat part of the Simon sleeve, about an inch short of contacting and locking into the lug. (I expected that to happen; was trying to understand better how the pieces of the barrel assembly and bayonet interact.)
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  4. #14
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    I went with a BCM A2X extended flash hider on my 14.5" Colt SOCOM barrel. My dad and I pinned and welded. I'd post a pic, but for some reason I have a hard time posting pic's here.

    NYH1.

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  5. #15
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    Quote Originally Posted by Diamondback View Post
    Question: Does an M4 bayonet normally index on the barrel, or on the FH? I just tried mounting an OKC-3S on the 16" C8, and all was fitting well until it bottomed out against the fat part of the Simon sleeve, about an inch short of contacting and locking into the lug. (I expected that to happen; was trying to understand better how the pieces of the barrel assembly and bayonet interact.)
    The ring of the bayonet sits on the rear of the flash hider on a 14.5” barrel (or a 20” or a 16” midlength). On a carbine with a longer barrel the bayonet lug is in the same place on the FSB so the ring of the bayonet ends up around the barrel itself when mounted on the gun. With a pencil profile, like on a Colt 6520 for instance, the barrel diameter is too thin to support the bayonet ring. I haven’t actually tried mounting a bayonet on a 16” M4 profile barrel because I don’t own one, but I suspect even with the added diameter it still isn’t enough to *properly* support the bayonet. Another issue is that the added length of the barrel on a 16” carbine overhangs more of the bayonet blade as well and renders it less useful for the intended purposes of a mounted bayonet.

    As far as the Simon sleeves on C8s go, I really don’t know much about them.

    EDIT: it occurs to me that if you are using the BCM C8 style barrel, I believe it is slightly longer than the actual military C8 SFW barrel. The military C8 SFW barrels are 15.8” I think and the BCM is at least 16”. So that might be why your bayonet isn’t fitting.
    Last edited by Circle_10; 02-03-20 at 09:43.

  6. #16
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    OP here...

    Thanks guys. I think i"ll go the BCM extended A2 route. It not much more than the ADCO spacer and it's drilled and comes with a pin.

    -Geo
    Live free or die trying!

  7. #17
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    BCM SOCOM Build.jpg

    Just had my buddy who works at my local gun store smith my 14.5 BCM socom upper with a free float KMR rail. Re-weld the A2X birdcage back on too all for $75.

  8. #18
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    Quote Originally Posted by Diamondback View Post
    Question: Does an M4 bayonet normally index on the barrel, or on the FH? I just tried mounting an OKC-3S....
    FH for sure. Specifically, as I understand it, with an old M7 bayonet mounted to a 20” M16 or a 14.5” M4, the bayonet ring sits just behind the rear groove of the A2 flash hider. You can get the same fit with a 16.5” middy. AFAIK, the M9 fits the same as an M7.

    From what I’ve read though, the grip of the OKC-3S is a smidge longer, so the ring ends up a little farther forward than an M7 does, but still on the rear part of the FH. I’ve never seen one in person, so I don’t know how much extra length is there, but I’ve heard a suggestion that it would fit on a 14.7 + A2.

  9. #19
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    It turns out that the OKC fits on my shimmed-to-14.7 M4-profile just fine. Next problem is figuring out where BCM spliced in the extra 0.3" on their SFW and sleeve... or finding out the corresponding measurement on an Eickhorn bayonet.
    <><><><><><><><><><><><><><><><><><><><><><><><>
    Ye best start believin' in Orwellian Dystopias, mateys... yer LIVIN' in one!--after Capt. Hector Barbossa
    Psalms 109:8, 43:1
    LIFE MEMBER - NRA & SAF; FPC MEMBER Not employed or sponsored by any manufacturer, distributor or retailer.

  10. #20
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    Extended A2 is what I did. If I ever move to a "free" state, I'd SBR it!

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