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Thread: How much does barrel fluting reduce weight?

  1. #1
    Boolit Master
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    How much does barrel fluting reduce weight?

    I have a recent rifle self build, that turned out a little heavier than I wanted. It is a custom 30-30 cast bullet rifle, on a 788 Rem action, with a laminate stock, and 24" barrel. With scope, I am in the 10 lb range. It's a little heavy for me for offhand shooting. The barrel was a blank, and after turning, I left it a little fatter than the stock barrel. Of course, I could turn it down some more, but fluting seems more interesting. I would like to lose a pound. Say, cutting 6 flutes, 14 inches long, for example. What would that add up to? I don't really know how deep I can go on the flutes, or even what size ball cutter I should use. Any input from any forum members who have fluted their barrels?

  2. #2
    Boolit Grand Master

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    You can figure this mathematically by 1st figuring the volume of 1 flute then with the weight of the barrel material in sq Inches you can get a quick close idea of wat you will remove. Most use a slitting type saw blade for this since it fives a nicer looking leade in and leade out of the flute. Usually around 3" cutter dia. A ball mill will cut a flute but its a more abrupt start and stop. The set up will be more involved than cutting the flutes. A lot doing fluting take many small fine passes of .005-.010 cutting around the barrel each pass to keep it even. A fixture makes this easier to do. A 3/4" X 6" plate for a base a rotary index on one end bolted down and a tail stock at the other. A hole to match tee slots ( normally around .625 dia) on center of plates a tapped hole, strap clamp, and screw jack to support center of barrel and hold. The center pin makes adjusting to straight easier and the center clamp deadens vibrations. This can be bolted down or held down with strap clamps.

    Fluting can look good remove weight and improve cooling. Doe right it is a positive way to accomplish this. Pushed hard or not right it looks rough and increases stress tremendously creating other problems.
    As for barrel harmonics Ive always been curious as to how "offsetting" flutes would work ( similar to a reamer where the flutes equal 360* but vary by 5*-10* rotationally). I am curious if this would lessen or break up the harmonics in the blank.

  3. #3
    Boolit Grand Master

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    Once the barrel is fluted take the shavings and weight them. Otherwise use your machinists handbook to calculate the weight of the metal per c/c and then calculate the area to be removed and viola!

  4. #4
    Boolit Grand Master
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    The above answers are correct. In addition to reducing weight slightly, fluting can improve cooling and make the barrel stiffer, for the same amount of weight, if done correctly.
    Last edited by Petrol & Powder; 08-01-2019 at 03:41 PM. Reason: clarification

  5. #5
    Boolit Master
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    I'm just guessing at the dimensions of your flutes, but try 18"L x 1/4"W x 1/16"D for starters, and let's assume four of them. This amounts to 1-1/8 cubic inches of steel. Steel weighs about 640/144 (4.444) ounces per cubic inch, so these flutes would remove 5 ounces from the weight of your rifle.

    You can refine the quality of the estimate by improving the dimensions of the flutes.
    Last edited by Tatume; 08-01-2019 at 01:36 PM.

  6. #6
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    First of all, let me explain that I am not a metallurgist or an engineer. Would someone explain in simple terms how removing metal in grooves "stiffens" a steel rifle barrel. I am not saying anyone is wrong, I just don't understand the science/thinking behind that method. Thanks in advance, james

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    Quote Originally Posted by TNsailorman View Post
    First of all, let me explain that I am not a metallurgist or an engineer. Would someone explain in simple terms how removing metal in grooves "stiffens" a steel rifle barrel. I am not saying anyone is wrong, I just don't understand the science/thinking behind that method. Thanks in advance, james
    it does not add stiffness. what it does is makes it stiffer than a thinner profile tube of the same weight. the stiffness is due to the diameter of the tube.

  8. #8
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    It doesn't... Here's a pretty good article: https://www.buckmasters.com/Magazine...hat-Does-It-Do

    If you take an two equal weight barrels, one fluted and one not fluted, the fluted barrel would be stiffer since it would have a larger maximum diameter. in other words, the material that was removed from the flutes was effectively moved farther from the center of the bore, so the barrel would be stiffer. These numbers aren't correct, but think of a 5/8" round barrel and a 3/4" fluted barrel that have the same weight. The 3/4" fluted would be stiffer. The 3/4" round barrel would be the stiffest, before it was fluted.

  9. #9
    Boolit Master
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    I recently spiral fluted the barrel blank stub for my Tikka Lite 223 Ackley project. One of the reasons I fluted it was to see if I could get the weight down to match the weight of the 23.4" factory barrel. The stub I was working with was a one-inch diameter 17.5" long unturned barrel blank.

    I did manage to get the weight down to very close to the factory weight but this was a few months back so I can't recall the exact numbers I came up with. I posted a thread on this project at the following link. It's kind of a long read but I seem to recall including all my mishaps including the weight numbers before and after I fluted the barrel.

    http://castboolits.gunloads.com/show...illing-to-Loan

    HollowPoint

  10. #10
    Boolit Grand Master
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    I went back and added some clarification to my prior post.

    Yes a fluted barrel can be stiffer than a non-fluted barrel, if the overall diameter is larger than the non-fluted barrel.

    By starting with a large diameter barrel and then removing material by fluting the exterior, you can reduce the weight of the barrel while maintaining nearly the same stiffness of the barrel prior to fluting.

    So, starting with two barrels of the exact same steel, the same bore diameter and the same length but one having a larger external diameter; the fatter barrel would be stiffer than the thinner barrel but the fatter barrel would also be much heavier. Now, if you flute the heavier barrel you may not be able to get it down to the same weight as the thinner profile BUT you can reduce its weight some. The fluted barrel will be considerably stiffer than the non-fluted barrel but it will be lighter than the original non-fluted heavy barrel contour.
    If done properly, you can remove a significant amount of weight while retaining a significant amount of stiffness. You also add surface area and therefore improve cooling of the barrel.

  11. #11
    Boolit Master

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    Quote Originally Posted by TNsailorman View Post
    First of all, let me explain that I am not a metallurgist or an engineer. Would someone explain in simple terms how removing metal in grooves "stiffens" a steel rifle barrel.
    I saw this subject addressed years ago.
    People argued that the flutes did indeed make the barrel stiffer/stronger.

    One guy asked that if that was true, why not cut the flutes all the way down to the bore diameter?

    The arguing stopped after that.
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  12. #12
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    The problem with flutes is consistency. There is always a tolerance and they can and will stack to adversely effect consistency as the bbl. heats up. I have a fluted heavy bbl savage, in my opinion they are more for looks than any real weight savings or accuracy improvements. They are shallow and narrow I doubt they removed more than an ounce or so.

  13. #13
    Boolit Master
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    Thanks guys for answering my question. I had suspected that for the fluted barrel to be stiffer than a non fluted barrel, that the fluted barrel would have to be larger to start with--diameter wise. What I am reading here is that is a true assumption. I could not imagine that 2 barrels say .650 in diameter, fluting one would make it stiffer than the unfluted one. To my mind by fluting the barrel, the over all effect would be reducing the diameter of the barrel by the depth of the flutes as well as the width. I don't see the advantage of say producing a .700 diameter barrel and then fluting it to reduce weight; cooling would be another matter. I think I would just rather go with a .650 barrel and save weight that way and it would cool a little faster than a .700 also. The .700 barrel would heat up slower than the .650 but it would cool down slower also. I have owned both diameter barrels in .30-06 and that has been my experience anyway, james

  14. #14
    Boolit Grand Master

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    One way to see it is to look at a piece of sheet metal that's flat its fot a lot of give bend and spring to it, just try to pick it up by 1 edge. Now add a bend to it lengthwise and pick it up form it round and its much stiffer. round with grooves around its circumference is even stronger. Adding shape to a piece with corners, radiuses, grooves does add stiffness.
    The body in your car with out the rolls folds and contours would be easily bent.

    One thing I would recommend ( especially if this is your first working with doing fluting) is to pick up a piece of cold rolled or even wood dowel and turn it to match barrel contour of the barrel and glute this first to see if its what you want and looks good to you. If you scrape this piece you aren't out the barrel and its cost. A piece of wood dowel done makes a good test piece, doesn't dull cutters and can be finished and made iton a rubber band gun or toy for family. Your going to be dealing with several set up points, start stop rotation depth and setting these on the dowel first is way easier

  15. #15
    Boolit Grand Master Texas by God's Avatar
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    I don't know much but I know there's no such thing as a LIGHTWEIGHT 788. Believe me, I've tried. Lots of steel in that action. That said, I do love them. I once considered miling a large flat on the barrel unseen under the forearm for weight saving but thought better of it.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  16. #16
    Boolit Grand Master

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    It isn't always just weight on a rifle balance point of the rifle makes a big part of how the rifle feels. Balance is a big part. Nit just weight but how its distributed between the hands.

  17. #17
    Boolit Master


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    Not to deviate from the subject but a couple have commented on changing the barrel on a 788.

    Is removing the barrel on a 788 any different than pulling one from a 700?

  18. #18
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    http://www.scorehi.com/flute.htm

    Fluting a #7 barrel with eight 3/16" wide flutes will reduce its weight by 14 to 16 ounces
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  19. #19
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    Can you post some pics. This sounds like my kind of gun. I have always wanted a 788 in 30/30.
    " If you cant do it with a 308 , you dont need to do it!

  20. #20
    Boolit Master
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    Here you go, my pride and joy. All 10 1/4 lbs of her.
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    Last edited by GBertolet; 08-11-2019 at 10:33 PM.

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