What's the BEST Barrel Length for 5.56 uppers?

Discussion in 'General Firearms Discussion' started by undeRGRound, Jun 4, 2015.

  1. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    ;)

    OK, I want a long range hunter, primarily for heavier "boolits", but "varmit" rounds would be a bonus. I may just put off the "varmit" barrel for later, so the thrust of this discussion will be 20" vs. 24" hunting barrels, for heavier bullets. Just wondering mainly if the extra 4" and weight is worth it.

    I have not found a good online opinion, so I'm asking the collective wisdom of HPFF :D
     
  2. Think1st

    Think1st Supporting Member

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    Not being a reloaded, I don't have the specific knowledge of powder burn rates for .223/5.56mm rounds to be able to make a recommendation based on those factors. I can, however, pose that as a consideration. From some of my reading on this site, it seems that .223 loadings don't exactly use slow powders. If that is the case, would the gasses still be expanding with enough force to accelerate the bullet as It travels a full 24"? If not, then 20" should suffice.

    The other factor to consider is bullet weight and the associated rate of twist. It seems that varmint rounds use 50-grain bullets. With that in mind, you will want to go no faster than 1:9.

    That's my humble $.02. Hopefully, this will give you some ideas and spur further discussions along these lines.
     

  3. USMC_VET

    USMC_VET Supporting Member

    If you want accuracy and reach out to 700 yards then get a 18" barrel . That's what is on the mk12 rifle which is,a light duty sniper rifle . Also using a 77 grain rd you will see sub moa at 100 yrds
     
  4. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    Specifics available in the OP, no 18" barrels unless you have additional info like Think1st was saying he lacked, 'Vet ;)

    I'll entertain the 18" but I definitely want the most velocity. Prolly excluded...
    Reloading WILL be part of the equation at some point, but that can be customized to the barrel in question. The standard military issue is 20" and it is likely a great starting point, the 18" barrels were most likely a compromise for a totally opposing set of circumstances than I am considering. I have 2 with 16" uppers now and 18" just ain't worth the dough for what I want to do...

    1. 20 inch merits and drawbacks
    2. 24 inch merits and drawbacks
    3. ...anything else had better be accompanied by huge amounts of data...

    :D
    Thanks for the input so far, but I have it narrowed down for good reasons!
     
  5. moona11

    moona11 King of you Monkeys Lifetime Supporter

    The 18" ain't a bad way to go. But the 20" bull barrel is better IMO. I don't think anything longer is worth it. The shooter makes the difference. Its all in the skill brother. I've seen snipers get out shot by farm boys and 13 year old ;-)
     
  6. USMC_VET

    USMC_VET Supporting Member

    A 18" barrel with 1/7 twist is great option for a AR
     
  7. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    BBTI only goes up to 18" :( so it is not any real help.

    Don't get me wrong, fellas, (USMC-Vet) I value your opinions but data will help a lot also. I'm a very scientific Mole ;)

    This means a lot, his experience dictates his opinion and he said that. A standard or pencil barrel might be fine in a 20" but varminting I think I would need a 24" fluted bull barrel. I'm thinking it's 2 different things for my purposes...
     
  8. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    But you are not telling me WHY!!!
    "Cuz I said so" don't cut it anymore, DAD! :rofl: :D
     
  9. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    your post came in whilst I was making the one after it, 'Vet...
     
  10. Rachgier

    Rachgier Administrator Staff Member

    Well, let's start more with some information from you. What do you want your range of "heavy" to be? We can start to tailor the specific information you are looking for with a better understanding of what you're looking for. The 1:7 is a great all around barrel that can shoot most everything in a shorter length and in the 18" Mk12 style Vet is referring to is scary nasty accurate with 70, 75, and 77 grain rounds. BUT it doesn't shoot 55's or 62's worth a damn. An 18" SOCOM or heavy barrel will stabilize up to the 90 grain bullets very well at just almost every single velocity offered in a commercial round for 70,75,77, and 90 grains. Hand tailoring the rounds yourself can squeeze out even more accuracy.

    As far as your barrel length, unless you want to dedicate it to a bench gun and aren't worried about carrying it anywhere, go for the 24". Otherwise I would focus on the 18-20" barrels with a 1:7 twist for heavier bullets at just about any velocity with scary type accuracy. The 20" barrel will easily give you AT&T to 1,000 yards with a custom tailored hand roll.
     
  11. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    I think we're narrowing it down now ;)
    I'm also thinking an 18" barrel is somewhat of a specialty size, and I can find a very similar item in a 20" for less, and get a velocity bump as a bonus. Barrel length is nearly a non-factor for accuracy, and sight radius will be completely useless because I intend to be strictly using it with a scope.
    I had always been under the impression that a 62 grain was still in the 1:7 range... is it something to do with the 18" length or other factor peculiar to the SOCOM barrel?
     
  12. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    Is this chart OK?
    Yellow means caution, or marginal performance, but the text below
    seems to be somewhat contradictory. :confused:

    [​IMG]
     
  13. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    I was thinking 69 gr and up, it fits everything it seems!
    (barrel, intended range in yards, and hunting use) It also seems to make a
    definite line between a 24" varminter barrel clear. Twist, length, grain, etc.
    ALL seem to show a definite "Philosophy of Use" difference. (POU, hat tip Nutnfancy)
     
  14. Rachgier

    Rachgier Administrator Staff Member

    The 62 grain is definitely in the wheel house of the 1:7 but they shoot better from shorter barrels for some reason. Also, accuracy is affected by barrel length but it's negligible until you reach out to competition distances. The SOCOM barrel is an HBAR with the grooves in it to accept an underslung grenade launcher. It stands up to FA better than a gov't profile barrel. It's a great compromise between a bull barrel and gov't profile barrels. At 16" it's about 4oz heavier.
     
  15. Rachgier

    Rachgier Administrator Staff Member

    Well that chart validates my prior assessment about the 62 grain being okay but not optimal in the 1:7. Like I said, if you want to go heavy, go 1:7. Length is up to you. Longer barrel, longer range but the gain from 24" to 20" isn't worth the added cost and weight.

    I would say, based on your information, that 18-20" barrel with a 1:7 will do exactly what you want it to do with room to go lighter as long as you understand the performance will suffer on the lighter side.
     
  16. Rerun

    Rerun Supporting Member

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    That's real funny because the AR-15, as designed by Eugene Stoner of Armalite fame, was released with a 1:14 twist rate barrel using 55 grn projectiles with 3150 FPS velocities that allowed accurate shooting out to 330 yards.

    Only after McNamara required the Army to use the AR-15, the re-named M-16 equipped with a 1:9 twist barrel and 55 grn projectiles with 3250 FPS velocities allowing accurate shooting to 500 yards was finally accepted by the US Army.

    eldar
     
  17. USMC_VET

    USMC_VET Supporting Member


    I knew you would post here sooner or later , thanks !!
     
  18. Think1st

    Think1st Supporting Member

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    The M-4 and M-16a2 have a 1:7 twist, and they use the 16" barrel. According to the Army TM, they are both rated at 550m for point targets.

    The M-16a1 had a rate of twist of 1:12 and was rated for 460m against point targets. I only remember this because I had to memorize it for one of the many Soldier boards that I did when I was enlisted. We also had the a1 models in basic training.
     
  19. undeRGRound

    undeRGRound ROLL wif Da MOLE! Supporting Member

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    Both of these statements were correct at various times. Both twist rates were specified for YAW after hitting a soft target. The 1:12 change was made to get a bit more range. Really interesting stuff!

    Thanks everyone, I can interpret data and numbers, but wondered how it shook out with experienced shooters, in the real world. I also found a decent thread in the arfcom archives that led me to the same conclusions.
     
  20. FlashBang

    FlashBang I Stand With Talon Lifetime Supporter

    Why not use a bolt action? A bolt action will give better accuracy in my experience. The added benefit is that it suppresses better should you ever wish to do that.

    .