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Thread: anybody have a good barrel length/velocity table for 556?

  1. #1
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    anybody have a good barrel length/velocity table for 556?

    I'm having a very hypothetical debate with myself about what barrel length to go for on my next carbine. I just sold my only AR (16" cav/cmmg middy)
    been shooting my glocks a fair amount... and i've always had a fascination with short rifles. so i'm thinking now that i live in the wonderful free state of colorado, i may build up an SBR sometime in the next year or so.

    basically longer is better for ARs as far as velocity and function go... so would a 12.5 be a good compromise? the 10.5's are cool, but what's the muzzle velocity? are they reliable?
    i probably will not be running a can any time in the near future.

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    I would say if you are going to do a SBR build, 10.5 or 11.5 would be a good selection for upper. I like the 12.5 because it will be able to fit my AAC Spr/m4 (and Noveske doesn't make a 11.5" bbl). I don't have any ballistic charts or tables but if this rifle is going to be used as a paper puncher get as short as you like, if it's for a SHTF/Self defense gun, go with the 10.5 or 11.5 as stated above. Anything longer kinda makes the process of NFA stuff not really worth it. You could also look into 6.8spc, that caliber is pretty good for keeping decent velocity from short bbls. It really depends on ammo as well, keep in mind this is my opinion and I don't have any actual facts to base this on, just my observations. Best of luck.
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  3. #3
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    A lot of people seem to like the 12.5" uppers, but I personally prefer 11.5" (Colt, BCM), 10.5" (LMT, Noveske, Sabre), or 10.3" (Daniel Defense, Colt). For me if I'm paying a $200 stamp I want something to be as short as possible. The qualifier to that statement though is it must still reliably function and maintain enough muzzle velocity to achieve the desired effects on the target (ie fragmentation) at the prescribed ranges an SBR is designed to be used at. The nice thing about the 10.5/10.3 is that since it is a standard issued barrel length for US forces it has been very carefully characterized and tested for function.

  4. #4
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    77 grain bullets still the hot setup for the short guns?

  5. #5
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    Im planning on trying the 70gr. Barnes TSX load that SSA offers out of my 10.5.
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  6. #6
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    Quote Originally Posted by skyugo View Post
    77 grain bullets still the hot setup for the short guns?
    Hornady 75gr 5.56 TAP is probably best.

  7. #7
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    Just a little side note. I built my SBR using a BCM 11.5" upper. It has Magpul front and rear sights. markm and myself went out the other day shooting again and I was easily able to hit a steel silhouette at approx. 220 yds. using both 55 and 62gr. ammo. I always get amused when I hear people say that shorties can't hit past xxxx distance. In the near future I may put my Leupold or ACOG on there and try some 300 yd stuff.

    My 14 year old was pinging away at the steel hanger set up at 100 once he found his niche.



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  8. #8
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    Page down a bit on this post. I have a barrel velocity chart listed there.

    http://m4carbine.net/showthread.php?t=38754
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  9. #9
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    Here is another from Wes at MSTN with 77gr.

    http://www.ar15.com/forums/topic.htm...f=134&t=149575

  10. #10
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    Quote Originally Posted by Iraqgunz View Post
    Just a little side note. I built my SBR using a BCM 11.5" upper. It has Magpul front and rear sights. markm and myself went out the other day shooting again and I was easily able to hit a steel silhouette at approx. 220 yds. using both 55 and 62gr. ammo. I always get amused when I hear people say that shorties can't hit past xxxx distance. In the near future I may put my Leupold or ACOG on there and try some 300 yd stuff.

    My 14 year old was pinging away at the steel hanger set up at 100 once he found his niche.
    I'm guessing most of the people who make claims about the "limited" external ballistics of SBRs have never actually tried it. I have a 10.5" LMT that can make well-centered hits all day long on 200 yard steel with both XM193 and 75 gr. Hornady (the latter making VERY well centered hits) using an Aimpoint Micro or irons. It actually shoots better than my 16" Colt. It's 80%+ on the 300 yard plate, and the misses are probably my eyesight and not the gun. The plates are about 12x18 inches, the 300 is a bit bigger.

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