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Fluted Barrels

Discussion in 'General Gun Discussions' started by repo, Nov 1, 2008.

  1. repo

    repo Member

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    What are the benefits of fluted barrels? I can see they would reduce weight but I only ever see them on target or bench rest guns so that seems redundant.

    The other thing I can think of is faster heat dissipation due to the larger surface area, but target shooting is pretty slow paced so again it seems redundant.
     
  2. USSR

    USSR Senior Member

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    The only real benefit is that it allows you to remove weight out on the front end of a rifle wearing a long, heavy contour barrel for rifle balancing purposes.

    Not all forms of target shooting are slow paced. F Class requires 20 shots plus however many sighter shot you elect to shoot within 30 minutes. But heat dispersion in and of itself, IMHO, is not a good reason to flute a barrel.

    Personally, I would only have a fluted barrel made as part of the cut rifling process, in which the barrel is fluted prior to the rifling being done.

    Don
     
  3. ieszu

    ieszu Member

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    Trying to figure that out....
    Fluting increases surface area, so a barrel does cool faster. It also reduces weight and maintains the structural strength of a bull-barrel the same diameter as the the outer-diameter of the flutes.

    If it is done correctly, it gives you a cooler, stronger barrel for less weight. The flutes must be indexed properly for even spacing, and should only be done by someone who knows what they are doing.

    What companies do this? From what I can find, even Lilja and Hart cut the fluting after the rifling is done, so that the profile is square to the bore. Not saying you are wrong, just curious who does it that way.
     
  4. USSR

    USSR Senior Member

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    Quote:
    Personally, I would only have a fluted barrel made as part of the cut rifling process, in which the barrel is fluted prior to the rifling being done.

    ieszu,

    Lilja and Hart both rifle their barrels using the button riflling method. With button rifled barrels, the fluting MUST be done after the barrel is rifled, and removing metal from the barrel exterior causes changes to the bore dimensions. With a cut rifled barrel such as Krieger, Obermeyer, and Mike Rock, the barrel is bored, then the barrel is fluted, and finally the bore is reamed and rifled. So, any changes to the bore thru fluting are irrelevant, since the barrel is reamed and rifled to the proper dimensions AFTER the fluting is done. This is why both my fluted barrels (Krieger and Obermeyer) are cut rifled barrels.

    Don
     
  5. koginam

    koginam Member

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    I have fluted between 150 and 200 barrels from just about every manufacture and not one has shot worse the before it was fluted, but none has ever shot better either.
    Maybe I have been lucky but I think its how I do it. I use a vertical mill with a carbide endmill, instead of the horizontal mill because it puts less pressure on the bore. I also cryo my barrels before and after machining
     
  6. ieszu

    ieszu Member

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    Trying to figure that out....

    Don - I understand now... completely forgot about companies such as Kreiger and Obermeyer. Thanks for the info.
     
  7. Howard Roark

    Howard Roark Member

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    Why?
     
  8. wally

    wally Senior Member

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    I was under the impression that the purpose of fluting was to increase barrel stiffness and reduce mass thereby changing barrel harmonics. If you can but a node at the muzzle accuracy will be much improved over a barrel that is near an anti-node at the muzzle.

    --wally.
     
  9. RockyMtnTactical

    RockyMtnTactical Senior Member

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    More surface area for better heat dispersion. Less weight.
     
  10. USSR

    USSR Senior Member

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    With button rifled barrels, the fluting MUST be done after the barrel is rifled,


    Don't know.

    The stiffness factor is probably one of the most misunderstood aspects of barrel fluting. Fluting a barrel does not make the barrel stiffer than it was prior to fluting (it is actually less stiff). When comparing the stiffness of barrels, you always compare two barrels of the same length and weight. For example, Krieger's #9 Heavy Varmint contour barrel weighs 6.5#, and if you take their #10 MTU contour barrel (7.0#) and flute it so it weighs 6.5# also, it will be stiffer than the #9 contour barrel that weighs the same.

    Don
     
  11. HammerBite

    HammerBite Member

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    Why button rifle before fluting ...

    This is just a guess, but I imagine that as you drag the button through the bore there will be a slight temporary barrel bulge that will follow along with the button. Since the thickness of the barrel wall is less under the flutes the amount of radial bulge will be greater under the flutes, with the result that the button will see less radial force under the flutes and will leave a shallower impression. The final groove depth will vary depending upon whether the groove is passing under a flute or a rib.

    Like I said, that's just a guess.
     
  12. dmazur

    dmazur Senior Member

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    Sorry to do a "I saw an article..." answer, but I just can't find the darn thing and I didn't save a link to it.

    Anyway, the article showed the effects of fluted barrels and the amplitude of barrel vibration, and the conclusion was that fluting doesn't help the barrel's accuracy at all. That is, fluting a barrel makes it less stiff. Laws of physics and mechanical engineering formulae describe it quite well. However, for barrels of the same weight, a fluted barrel has less vibration amplitude.

    So, if you're going to have a barrel that weighs x lbs, if you flute a heavier (larger diameter barrel) so that it now weighs x lbs, it will be slightly more accurate than an unfluted barrel that weighs x lbs.

    The misunderstanding is that you can improve the accuracy of a barrel by fluting it. That just isn't true.
     
  13. USSR

    USSR Senior Member

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    Not "slightly more accurate", just slightly more stiff. Fluting, when done correctly, does not directly impact whether or not a rifle is accurate. Accuracy is more a function of the quality of the barrel and chambering, bedding, and the load used (to say nothing of the shooter). I shoot two rifles with fluted barrels in 1,000 yard F Class competition, and have not been handicapped in any way.

    Don
     
  14. ridata

    ridata Member

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    I personally think fluted barrels look sweet, and would buy a fluted over a non-fluted for that reason. The Ruger MkIII in specific.
     
  15. Larry E

    Larry E Member

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    The only reason I can see to flute a barrel is to make weight on a competition benchrest rifle, otherwise it's money better spent on something else. :eek: I've got one rifle with a fluted barrel and that's because it came from the factory that way and most importantly had the rifling twist I wanted.
     
  16. Ridgerunner665

    Ridgerunner665 Senior Member

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    Digging up an old thread so me and Maverick223 can finish our discussion...

    Maverick,
    You seem to think that when you reduce the weight of the muzzle end of the barrel it makes the barrel stiffer...it doesn't.

    http://www.varmintal.com/aflut.htm

    More info on barrel dynamics...
    Barrel dynamics... http://www.varmintal.com/apres.htm
     
  17. Russ in WY

    Russ in WY New Member

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    IMHO if you are relying on the flutes for cooling , your in for a long wait, and the brl is probably way to hot already. My 2¢ Russ.
     
  18. Jim Watson

    Jim Watson Senior Member

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    One barrelmaker said the main advantage of a fluted barrel was $50 more in his pocket.
     
  19. Ridgerunner665

    Ridgerunner665 Senior Member

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    Jim,

    Thats exactly the point I've been trying to get across.
     
  20. MachIVshooter

    MachIVshooter Senior Member

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    to understand the advantage of fluting, try not thinking of it as removing material from a large diameter barrel, but more as gusseting a smaller diameter tube.

    As with anything structural, you get more rigidity for the same weight by making perpendicular or radial protrusions from the core structure. Take a piece of 1/4" round stock and bend it-pretty easy. Now take an X shaped piece of steel, weighing the same, but comprised of 4 fins perhaps 1/16" thick by 1/4" wide. Not so easy.

    As has been pointed out, it will be more rigid than a solid barrel of equal mass & length, but less rigid than a solid barrel of the same diameter.

    I only have one rifle with a fluted barrel, my Remington 700 LVSF. It has a medium contour barrel, yet weigh less than a standard 700. Average 100 yard accuracy is .7 MOA, with some handloads producing < .5
     
  21. ArmedBear

    ArmedBear Senior Member

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    Exactly. The point is to stiffen a lighter barrel.

    I don't know why a bench gun would be fluted, really, but if it's carrying or for offhand shooting, fluting can make sense.

    To get light weight, you can do one of three things:

    1. Turn the barrel down to "pencil" diameter.
    2. Keep the barrel a standard contour, but flute it to lighten it up.
    3. Use high-tech materials, other than a regular steel barrel.

    All three are used and have their merits, but #2 offers a lightweight barrel with good rigidity and a reasonable price.

    For bench shooting, there are some designs that increase the surface area (multiple spiral flutes, for example) for heat dissipation. I have no idea if they work. Some just look cool, for those who prioritize that. There are multiple options for the 10/22 crowd, for example.:)
     
  22. hammerklavier

    hammerklavier Member

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    How about a triangular barrel?
     
  23. MachIVshooter

    MachIVshooter Senior Member

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  24. Corey

    Corey Member

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    +1 to what Ridgerunner665 said.

    As for increasing cooling of the barrel, fluting a rifle barrel makes such a small difference in cooling that it is difficult to measure. The heat transfer coefficient of an object determines how fast it cools. For a rifle barrel you can approximate by using the formula for heat transfer coefficient of pipe wall. hwall = 2k/diln(do/di) where k is the thermal coefficient of the material, di is the inside diameter of the barrel, and do is the outside diameter of the barrel. If you double the outside diameter of the barrel you will have 8 times the surface area on the outside, but no change on the inside. This formula tells us that doubling the outside diameter of the barrel gives you a heat transfer coefficient only 1.3 times greater. Therefore an 800% increase in surface area gives about a 30% increase in cooling. I don't think barrel fluting increases the surface area by anywhere close to 800%.

    Most armies around the world started the WW1 with air cooled machine guns using fluted barrels to increase cooling thus allowing higher rates of fire (or so they thought). Water cooled machine guns that were used then are a different situation. By the end of WW1 almost no machine guns were being made with fluted barrels. They must have figured out that any perceived benifit did not outweigh the manufacturing costs.;)

    To me, the only reason for fluting a barrel is cool factor:cool:. That said, I do like how fluted barrels look on some types of rifles:)
     
    Last edited: Dec 30, 2009
  25. HGUNHNTR

    HGUNHNTR Senior Member

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    The main reason is that it looks COOL, and COOL sells guns.

    Heat dissipation, stiffness, whatever there are plenty of obscenely accurate rifles out there with non-fluted barrels. The main draw is hooking you, the customer, and getting you to part with your $$$$ happily.
     

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