Question on AR fluted barrel

Discussion in 'AR-15 Discussion' started by Dzscubie, Apr 7, 2010.

  1. Dzscubie

    Dzscubie New Member

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    Ok, I need your expertise AR gurus out there. What is a fluted barrel for and what is the reason for having one on an AR . I have seen more and more of them popping up but like the boogaloo, it plumb evades me. :confused:
     
  2. Dillinger

    Dillinger New Member

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    JD here, and definitely NOT an expert.

    The theory behind the fluted barrel was two fold. 1) Save on front end weight and get the balance back closer to the grip. 2) The cutting of flutes are supposed to help the barrel cool more evenly. Whatever.

    Look, a bull barrel is a bull barrel for a reason. You want tack driver accuracy.

    Now, when someone buys a heavy barrel weapon and has to hump it places, they want to start cutting weight out of the thing. Blasphemy in my opinion, but what do I know?

    So, someone came up with the idea of cutting flutes down the barrel to shave weight, keep the bull barrel profile and "rigidity" ( because the whole barrel is not fluted ) so you have the best of both worlds.

    Now, I am not a small guy. If I spec a rifle, I spec a rifle weight and I expect to have to carry it. I can't see myself EVER getting a bull barrel and then fluting the hell out of it to get weight down.

    But that is me. A lot of people request it. It's very popular in both the Hunting World and the AR Varminting world. If you have a mill, you can set up the barrel vice and do 5 or 6 or 7 in just a day or two depending on the number and depth of the flutes and make a nice profit for the week.

    It's all preference my friend. Everyone likes what they like.

    JD
     

  3. Dzscubie

    Dzscubie New Member

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    Thanks JD I knew I could count on you.

    I was asked this by one of my officer and I was ashamed to say I really did not know what the flutes were for. We did discus the quicker cooling idea but did not know that it was a bull barrel with the flutes cut in it.

    I don’t feel I would want one but, as you say, different people like different stuff.

    Thanks again
     
  4. Dillinger

    Dillinger New Member

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    Scubie - A barrel does not have to have a "bull" profile to be fluted, it's just the most common.

    The depth of the flutes is determined by the thickness of the barrel wall.

    If you have a thin, or tapering, barrel profile then the flutes can be very shallow or they can taper along with the profile to match.

    The end result is usually a reduction in weight. Rarely do we have someone comes in that wants shallow flutes cut for "style" purposes. :cool:
     
  5. Car54

    Car54 New Member

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    JD, do you know if fluting has any effect on accuracy or bullet spin?
     
  6. Dillinger

    Dillinger New Member

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    That is subjective Car. Very, very subjective depending on which side of the fence you stake your tent.

    One of the big things that affects accuracy is harmonics induced on the barrel by the explosion of the round being touched off and the gas pressure being released, especially from one round to another.

    Now, take a magnum caliber like a .300 Win mag. Massive round, traveling at incrediable speeds and ground zero to a small explosion when you touch it off.

    Take that round and put it along side a .22LR

    Which one is going to induce more pressure on the shooter through recoil? Which one is going to generate more force on the action?

    Obviously the .300 Win mag is going to do everything with more aggression.

    So, put them both in an identical metal cylinder and ask that cylinder to take that force and convert it to torque to spin the bullet. Then take that cylinder and rest it on top of something like a car tire that rotates on an axle. Round and Round.

    If the walls of the cylinder are paper thin, and it weighs only a few ounces, what will happen? You touch that round off and the .22LR is going to give the thin cylinder a little spin and the .300 Win is going to spin it like a top.

    If the walls of that cylinder are as thick as battleship armor and it weighs dozens or hundreds of pounds, what will happen? The .22LR probably isn't going to cause the wheel to move at all, and the .300 Win Mag is going to cause VERY little movement.

    That is basically what happens when you touch off your round. You induce MASSIVE torque into the barrel via the lands and grooves to get the bullet spinning on it's axis to cause rifling.

    Have you ever taken a drill and put a large caliber drill bit through a piece of metal and have it BITE?? What happens to your wrist??

    Just food for thought.....

    JD
     
  7. NY Marksman

    NY Marksman New Member

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    Fluting will not have anything to do with accuracy but as said before it will aid in cooling and weight reduction. I have an 18 inch Stainless Steel fluted Sabre Defense barrel and it is extremely accurate.

    [​IMG]
     
  8. Dillinger

    Dillinger New Member

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    While you may personally believe that, I would challenge that statement on any shooting range in the world with rifles produced to the exact same specs, having the only difference be a true bull barrel versus a fluted barrel.

    But that is my personal belief based on experience that I have personally seen.

    JD
     
  9. Car54

    Car54 New Member

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    Boy do I feel stupid. I was assuming that the fluting was inside the barrel in addition to the rifling.
     

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  10. ThorsHammer

    ThorsHammer New Member

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    I figured it wouldn't make a smack of a different since I am not rifleman enough to out shoot either type of barrel. Makes sense on the bull barrel though, the added weight adds to controllability of the rifle.
     
  11. 753X0

    753X0 New Member

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    Last edited: Apr 8, 2010
  12. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

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    If you take a bull barrel and flute it (properly) you will not affect the accuracy much, if at all. It will not get more or less accurate, it will simply get lighter. Some theorize a fluted barrel is MORE rigid than a comparable unfluted barrel. I do not believe this to be true. A fluted barrel is probably more rigid than an unfluted barrel of equal weight and consequently (potentially) more accurate.

    There is more surface area on a fluted barrel so it should cool better, but the cooling effects may be overrated.
     
  13. NY Marksman

    NY Marksman New Member

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    You are of course welcome to your own opinion and me to mine but I have some experience in this particular subject myself, which is one of the main reasons I opted for a fluted barrel. If you would go to Sabre's website (Sabre is well known as one of the top tier barrel manufacturers) and take a good look at the section on barrels you will notice that with the exception of their tactical barrels, every one is fluted including the competition barrels. I'm pretty sure that they have done enough research to know whether or not fluting would or would not negatively effect accuracy. I have had both fluted and non fluted barrels and both will shoot much better then most of the shooters who own them. I still maintain that other then weight and cooling, flutting is a non issue.
     
  14. Dillinger

    Dillinger New Member

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    And we can agree to disagree, which I am fine with on this issue as it is HIGHLY subjective to who is doing the talking.

    Sabre is a high end AR manufacturer. No argument there.

    They are NOT a high end BARREL manufacturer. No one is ordering a "Sabre Barrel" for their AR to take to Nationals or to a 3-Gun. Why??

    Because Sabre is selling you a barrel that THEY believe is one of the best.
    Sabre is a BRAND built on a very quality assembled AR from the ground up, which happens to include a barrel that they have decided is the best FOR THEIR PRODUCT.

    I have no doubt that your fluted 18" barrel (I believe from reading your posts) shoots as well as anyone here can shoot it. I believe that you did your research and that you feel that barrel is absolutely the best for your needs. Absolutely no argument from me there. There is NOTHING wrong with a SABRE barrel.

    However, let's stick to the facts here for a moment.

    Sabre uses Button Rifling, according to many sources. There is nothing wrong with that.

    But Single-Point, Cut Rifling is the gold standard by which others are judged.

    Now, 5R is making a play for the top competitor, and as I have a rifle in the shop getting a 5R barrel I will let the forum know the results of that experiment.

    But right now, Single Point, Cut Rifling is the end all beat all.

    Now, as to the question at hand: Does Fluting Make a Difference In Accuracy.

    This is HIGHLY subjective as I have stated numerous times because there are "experts" on both sides of the fence.

    I have personally had a bull barrel rifle that I had "properly fluted" by my gunsmith of whom I also shop rat for and respect a great deal. The weapon dropped a ton of weight, but the even though it was the same ammo ( Federal Gold Medal Match of which the chamber was cut for using a brand new reamer ) and the same shooter ( me ), I noticed a difference in the grouping ability of the rifle. The barrel was a Krieger and the caliber was in a .308

    At the end of the day is the average shooter going to notice a level of accuracy changed by fluting on an AR type of weapon? No, not in the least.

    But everything being 100% equal, I have personally seen a difference with proper fluting affecting accuracy on a very, VERY good rifle.

    JD
     
  15. gman89

    gman89 New Member

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    Sorry to revive this topic, but I came across some information which might provide a different perspective on this issue. According to a handbook on firearms and ballistics I've been reading, the point of fluting is to aid in extraction for blow-back firearms (like the H&K P7 which I believe is fluted).

    "Fluted chambers are longitudinal flutes which are deeper at the forward end of
    the chamber and taper off towards the rear. These allow the gases produced on
    firing to flow back over the outside of the cartridge case during firing. This
    counters the internal pressure and ‘ lubricates ’ the case, thus facilitating the
    extraction process. This is utilized in blowback and delayed blowback weapons
    where pressures are relatively high, thus making extraction difficult" (Firearms and Ballistics, B.J. Heard).

    Having said that it still doesn't explain why it would be useful for other applications mentioned previously.
     
  16. Dillinger

    Dillinger New Member

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    gman - That is talking about internally in the chamber. The flutes we were discussing in this thread are on the OUTSIDE of the barrel.

    Two different animals. ;)

    JD
     
  17. c3shooter

    c3shooter Administrator Staff Member

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    Car 54, don't feel too bad- there ARE firearms with a fluted CHAMBER. Makes really funky marks on fired brass.
     
  18. Quentin

    Quentin New Member

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    Anyway, it was nice to see this older thread. Thanks for the excellent explanations JD. Very informative as usual.
     
  19. USEBOTHHANDS

    USEBOTHHANDS New Member

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    i can see both points of the argument on accuracy: on one hand you have a solid barrel (bull), with full spine (heft of extra metal), then you have a fluted barrel, NOT NECESSARILY WITHOUT full spline, but without the heft of extra metal.................that being said, i would reason that the "spine" would change the accuracy by changing the harmonics, and depends on how many, and how close together the flutes are spaced.

    lets use numbers:

    a bull barrel has a spine "strength" of say = 100;

    a fluted barrel of 5 flutes has strength of = 80;

    a fluted barrel of 6 flutes has strength of = 65;

    a fluted barrel of 7 flutes has strength of = 50;

    so in a way, you ARE losing NOT JUST WEIGHT, BUT SPINE TOO, THUS CHANGING HARMONICS.

    as for the normal shooter noticing the difference, it is most likely accurate enough.

    but with JD, he knew what his particular barrel WOULD do before having it fluted, and after fluting, HE noticed that it wasn't holding the same pattern............he knew his rifle, and knew what it should've been doing.................CHANGE IN HARMONICS OF BARREL = ACCURACY PROBLEMS.

    my $.02