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Thread: XM556SBCT3 in 16" barrels

  1. #1

    XM556SBCT3 in 16" barrels

    I have some XM556SBCT3 on hand I'd like to vet in my rifles. From what I gather, this is XM556FBIT3 from Doc's list optimized for 11.5" SBRs. Would it still provide adequate terminal performance in 16" barrels inside, say, 100 yards?

    Apologies to those sick of discussing the minutiae of this family of rounds, but I'm not exactly a ballistics genius.

  2. #2
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    Quote Originally Posted by ArgentFix View Post
    I have some XM556SBCT3 on hand I'd like to vet in my rifles. From what I gather, this is XM556FBIT3 from Doc's list optimized for 11.5" SBRs. Would it still provide adequate terminal performance in 16" barrels inside, say, 100 yards?

    Apologies to those sick of discussing the minutiae of this family of rounds, but I'm not exactly a ballistics genius.
    The FBI, which mostly uses XM556FBIT3 has both 11.5" guns and 16' POW guns in use with the same ammo.

    Based on my experince with the .223 equivilent, XM223SP1 in 11.5", 14.5'' duty guns and 16 " personal guns on hogs, I would not worry about it.

  3. #3
    Quote Originally Posted by ArgentFix View Post
    I have some XM556SBCT3 on hand I'd like to vet in my rifles. From what I gather, this is XM556FBIT3 from Doc's list optimized for 11.5" SBRs. Would it still provide adequate terminal performance in 16" barrels inside, say, 100 yards?

    Apologies to those sick of discussing the minutiae of this family of rounds, but I'm not exactly a ballistics genius.
    Looking at Doc's duty round stickied thread, I don't see that load or particular loads for SBRs. Is this information in another thread? I am curious about this load as well mk318 and how they compare to each other. Thanks.

  4. #4
    Quote Originally Posted by dtrice View Post
    Looking at Doc's duty round stickied thread, I don't see that load or particular loads for SBRs. Is this information in another thread? I am curious about this load as well mk318 and how they compare to each other. Thanks.
    I bought a case of XM556SBCT3 a year ago and did some research then but I didn't keep very good notes so bear with me here. EagleEyeGuns and Bonefrog, the two places XM556SBCT3 is most commonly available, agree it's equivalent to XM556FBIT3. Target Sports also occasionally sells this round:

    https://www.eagleeyeguns.com/product-p/xm556sbct3.htm
    https://www.bonefroggunclub.com/prod...ded-xm556sbct3
    https://www.targetsportsusa.com/fede...3-p-78478.aspx

    A few comments here on PF:
    https://pistol-forum.com/showthread....374-XM556SBCT3
    https://pistol-forum.com/showthread....39#post1081539

    I also recall this thread:
    https://www.ar15.com/forums/AR-15/FB...ng-/16-743010/

    Unfortunately none of these are official word from Federal, but I deduced XM556SBCT3 is XM556FBIT3 optimized for "SBC" 11.5" Short Barrel Carbines using the same "T3" bullet. I have been wrong many times before.

    Also as I recall, Mk318 isn't favored when options using the TBBC bullet are available:
    https://pistol-forum.com/showthread....18-SOST-bonded
    https://www.lightfighter.net/topic/s...iber-gel-tests

    I very much welcome corrections here.

  5. #5
    Personally, I would have no concerns using XM556SBCT3 in a 16" barrel.

    I actually would feel quite well armed with that ammo. ( Provided accuracy was up to snuff )

    I would strongly suggest a "real" 5.56 chambered AR.. with a nice long throat, to help keep chamber pressures manageable.

    Bone Frog Gun Club warning... NOTE: NOT for use in 223 REM chambered guns.

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