fluteing ?

Discussion in 'Gunsmithing' started by sams57, Dec 24, 2007.

  1. sams57

    sams57 Well-Known Member

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    would it be possible to flute a 26" varmint barrel to get rid of excess weight , and still keep the stiffness in the barrel? i would like to remove a pound if possible the # of flutes dosent matter to me. thanks , loader
    and merry christmas
     
  2. royinidaho

    royinidaho Writers Guild

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    Yep, but talk to someone who knows about barrels that have been fluted "after" installation.

    There may be some special considerations.:confused:
     

  3. James Jones

    James Jones Well-Known Member

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    Fluting a barrel after its been shot and broke in is not the best idea especialy if its a factory forged barrel or a button rifled , its still not a good idea to flute a cut rifled barrel after its been finish lapped unless you making very shallow flutes which is not gonna give you any weight reduction to speak of.

    When button rifled or forge rifled barrel are made they use a tremondus amout of pressure to either beat the barrel down into the mandrel that has lands on it to make the grooves or they push or pull a carbide button through the bore and that basical "irons" the lands and grooves into place , both of these processes put a great deal of stress into the barrel and if you go removing metal from it the barrel will move around and if the bore happens to open up even a couple tenths (.0002) the barrel will likely be a poor shooter. Companies that make barrels this way , flute their barrel , after they are bored and rifled but before they are finish lapped , the final lapping after the fluting will bring the bore dementions back into the same plane if the bore has moved.
    Barrels that are cut rifled like Rock Creek , Kreiger , Bartlein , and a few others use a single point broach that removes the material where the grooves are gonna be this process doens not induce any stress into the barrel their for they are far less likely to "move" during fluting , BUT , as far as I know they still lap their barrels after they are fluted. I talked to Mike Rock about how he flutes his barrels so deep with such huge flutes to get maximum weight reduction and he told me that he drilles the barrel out , flutes it then goes through the rifleing process this insures that the lands and grooves would have any added stress to deal with after they are made ,if this is truely the way its done their I believe this is the best method I've heard of , I have one of his heavly fluted barrels on a tactical 308 and it shoots as well as any other gun I've seen built with a Rock barrel (awsome)

    Its commonly said that a fluted barrel is more stiff than a none fluted barrel this is both true and false. A barrel that is 26" long , weighs 5lbs and is fluted will definatly be stiffer than a none fluted barrel thats 26" long and weighs 5lbs , this is because the fluted barrel will be larger in diameter and the fatter a barrel is the stiffer it is.
    Now if you take a #8 conture barrel thats 26" long and fluted then compair it to a barrel that is the exact same conture but not fluted the non fluted barrel will be stiffer every time , its impossible to remove material from a cylinder (other than making it shorter) and have it more stiff than it was before.

    Back to your question , you can roll the dice and take a chance that your barrel will shoot as well as it does now after its fluted but if it doesen't you just wasted $100-$150. I personaly would not risk it. Some guys can flute a bigger barrel like a #7 and remove as much as a pound and thats alot , if a guy were to come to me and ask me to make his gun lighter the barrel would be the last thing I'd mess with and when it came time to cut weight their I cut off 2" of the muzzle , you will likely loose more weight AND the gun will probably shoot better , because the shorter barrel will be stiffer and probably have a better crown , yes with some rounds their might be as much as a 150fps loss in velocity but this is generaly only with the big over bore mags like the 300RUM but I seriously doubt that any animal would be able to tell that the speed had dropped a little.

    Sorry for being so long winded but I just wanted to give a full explanation for why I thought it was a bad idea
     
  4. sams57

    sams57 Well-Known Member

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    thank you for the information. dont want to shorten the barrel so i guess i will have to live with it. loader
     
  5. James Jones

    James Jones Well-Known Member

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    What caliber is it?? , generaly cals in the regular mag range will only drop 20-40fps per inch , unless its already short.

    Hell sounds like a great reason to rebarrel ;)
     
  6. sams57

    sams57 Well-Known Member

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    james it is a 300 wsm, it is m long range ground hog gun, but it is soon to become my medium to loneg rg. elkgun [750-1200yds] that is why i realy dont want to cut it. i'm 59 and wanted to reduce the weight for hiking in the western mts. thanks, loader
     
  7. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Sams,

    I did an experiment on a cut rifled barrel, it was a Lawton 338 cal/ med contour/ 33" long. I wanted to remove some weight and add the cosmetics that fluting brings to the rifle. I made two passes on each flute, rather deep 1/2" ball end mill type. After it was done i re-installed the barrel for testing, groups were in the 3/4moa range, before it was around 1/4moa...so a change had occured. I got busy with other projects and didnt get back to it.

    Later on John at Broughton barrels called to chat about my rifles and chamberings i was using. Deep into out conversation i mentioned to him what i had done to the bbl i fluted and results. He said there is nothing wrong with fluting a cut bbl after its finished but you have to be careful and take lots of shallow cuts, and even with that you may need to stress releive the bbl and re-lap it. He told me to lightly lap my bbl and give it a try.

    I used some light polishing compound for about 50 strokes. I cleaned the rifle and used my barrel breakin sequence. The groups returned to .2moa

    I would not flute a button rifled barrel after its finished.

    I wont flute a cut bbl either as it takes too much messing around. Just order a new barrel pre fluted, cheaper in the long run.

    Dave
     
  8. koginam

    koginam Well-Known Member

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    You might consider stress reliving the barrel before fluting, this can be done by cryo or by heat. I use cryo but it is expensive when done right. Heat is inexpensive in comparison, i use an old pottery kiln but if the barrel will fit into an oven you could do the same thing , on a 1 inch dia. 26 inch long barrel 300 degrees for 13 hours should be enough to stress relive the barrel.
    i base this on personal experience.
    I would do the fluting on a vertical mill it applies less pressure on the bore.
    Good luck
     
  9. sams57

    sams57 Well-Known Member

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    thank you all for your feedback it has beeen very useful. loader
     
  10. Rustystud

    Rustystud Well-Known Member

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    Fluting barrels

    Have your barrel maker stress relieve the steel first. Yes, I know the steel maker says it is stress relieved from his shop. Don't believe it. Drill the barrel, stress relieve the barrel again. Then flute the barrel turning it 180 degrees, between passes. Now stress releive the barrel again. Lapp the bore, and button or cut the rifling. Turn the contour and stress relieve again. All the better button barrels are stress relieved at least 3 times. The process is different with cut rifling.

    Thre are three methods of stress relieving, heating in a heat treating oven, vibratory bead method, and cryogenic. Not being an engineer I can't say which is best or if a mix or match combination is better. I can tell you the top barrel makers will all agree that stress and heat are the bigest enemies to a barrel and accuracy.

    I highly reccomend talking to the barrel makers themselves. They will not let out their propriatary trade secrets, but they will give you the basics.

    Rustystud
     
  11. koginam

    koginam Well-Known Member

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    Many years ago I would buy barrels from J.P. Campbell he made barrels mainly for his own customers but he made a few to sell as well, He used the heat treat method to relive barrels , they were relived before any machining, after drilling, after reaming, after rifling, and again after contouring. 300 degrees for 13 hours each time. Of the 20 some barrels I bought from him I never had one that didn't shot great and no stringing.

    You didn't see much fluting back then but I think he would have done it after fluting as well.
     
  12. RAINIERRIFLE

    RAINIERRIFLE Member

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    fluting

    i flute barrels all the time for people. and have never herd someone say their berrel doesnt shoot good. you will have to work up dif loads as the barrel is stiffer and will have dif harmonics. all the things about stress relief and changing dimentions is all true but the bottom line is it doesn really effect accuracy that much.
     
  13. James Jones

    James Jones Well-Known Member

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    How does fluting a barrel make it more stiff ?

    And how does enlarging the bore not affect accuracy ?
     
  14. RAINIERRIFLE

    RAINIERRIFLE Member

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    Fluting

    you see button barrels come out all dif dimension the good ones come out tight and are laped into dimension. +/- this is why we need to use dif pilots on our reamers. what i am saying is fluting really doesnt get a barrel out of dimension unless it was borderline large to begin with. i flute and light lap after,