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5.56 SBRs - terminal ballistics

Discussion in 'NFA & Class III Discussion' started by MBB, May 12, 2011.

  1. MBB

    MBB Sharpshooter

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    So I see a lot of 5.56 SBRs, some with REALLY short barrels, and I have to wonder, how do these short barrels affect terminal ballistics? At what point, if any, would 9mm SBRs become more effective?

    Here (http://ammo.ar15.com/ammo/project/term_fragrange.html) is some info on military 5.56 ammo. I wonder how commercial self defense rounds are affected?
     
  2. 338Shooter

    338Shooter Sharpshooter

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    I would say with the heavy 75gr + PD loads you're still going to have better terminal ballistics than a 9mm, but I don't know. Military 5.56 has bad enough terminal ballistics out of a 20" gun making it hard to compare.
     
  3. Hump66

    Hump66 Sharpshooter

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    I seem to remember on Top Sniper II that the Pittsburgh Swat team guys said they use an M4 Commando (10.3" barrel) out to 600 yards.
     
  4. MBB

    MBB Sharpshooter

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    I have no doubt heavy-for-caliber rounds are accurate at that distance, but I wonder what kind of expansion/fragmentation results (ie terminal ballistics) are available at that distance (or any distance with ultra short barrels) other than a 0.22" diameter hole?

    I wonder if anyone has done any testing or has any data?
     
  5. carready

    carready Sharpshooter

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    From what I found, the 75gr TAP has a fragmentation range of about 50 yards out of a 10.5".
     
  6. HiredHand

    HiredHand Sharpshooter

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    Have you checked out the terminal ballistics section on m4carbine? Seems like somebody like, DocGKR, could give you an answer.
     
  7. MBB

    MBB Sharpshooter

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    Thanks, good info.
     
  8. english kanigit

    english kanigit Sharpshooter

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  9. Fyrtwuck

    Fyrtwuck Sharpshooter

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    I'm sure that there are some effects on terminal velocity with a shorter barrel. I have two SBR's. One with an 8" barrel and one with a 10.5. For my purposes, 200 yards or less, I think it will work just fine. I just bought an upper with a 7.5 barrel that I'm going to have to try out.
     
  10. MBB

    MBB Sharpshooter

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    Yes! Awesome. Great info.

    My summary: it seems even the Mk 262 stuff wasn't fragmenting as well as they'd like out of the 10.5" barrels so they went to an expanding bullet "optimized" for SBRs with a lower velocity expansion threshold hold. Great.
     

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