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Barrel fluting

Discussion in 'Gunsmithing and Repairs' started by rlpinca, Dec 25, 2002.

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  1. rlpinca

    rlpinca Member

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    Is barrel fluting a good idea for the extra money that is involved? I'm asking in specific for an AR15 that will occasionally see some rapid fire.

    What I know so far is that it increases surface are in order to provide faster cooling. It also decreases weight a little bit.

    I've also heard that it stiffens the barrel quite a bit and helps out in the accuracy department. The critics claim that the fluting process induces alot of stress into the barrel and can actually harm accuracy. They also claim that the increased cooling and the weight savings don't justify the extra money and possible extra stress.

    I'm just wondering if it's worth the extra money or if I'd be better off spending that elsewhere.
     
  2. Wildalaska

    Wildalaska member

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    The only downside to fluting is the stress it causes to the barrel. What we do after fluting is simply have the barrel cryo'ed..that releives the stress..

    Fluting is excellent for AR15 barrels and M16s,,,
     
  3. George Stringer

    George Stringer Member

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    As Wildalaska said it can introduce stress into the barrel but I've done several that showed no signs of it. It is still a good idea to have them cryoed after fluting. Fluting doesn't make a barrel stiffer. But a fluted barrel will be stiffer than an unfluted barrel of the same weight because you started with a heavier barrel. George
     
  4. rlpinca

    rlpinca Member

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    Thanks guys. I was just wondering about that. I'm looking around for an ar15 and have been seeing mixed opinions on it.
     
  5. Art Eatman

    Art Eatman Administrator Staff Member

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    You can go back to TFL and look under "The Wisdom of Gale McMillan". The caveat is that I don't know if cryogenic treatment was in vogue when he made his comments.

    Art
     
  6. larryw

    larryw Member

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  7. mete

    mete Member

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    As a metallurgist I am amazed that so many have been duped by the cryogenic myth. In all my years as a metallurgist if we wanted to stress relieve metal we HEATED it. Some of the barrel makers such as Shilen will tell you the facts but others such as Krieger will gladly take your money. Any machining can introduce stresses though if care is taken those stresses wiil be minimal. I'll be happy to answer any questions about cryogenics.
     
  8. Badger Arms

    Badger Arms Member

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  9. jrhines

    jrhines Member

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    Well said mete...

    I would be interested in your views on the cryo treatment . I am a machinist and do a bit of smithing, including heat treating. All of mine is done in a muffin furnance, none in anything cooler than my quinch tank.

    This might be a topic of a new, intresting thread.

    J Rhines
    Seneca, MD
     
  10. Wildalaska

    Wildalaska member

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    Cryo

    Mete, Id like to hear your views on cryo also...
     
  11. Nero Steptoe

    Nero Steptoe member

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    Mete, I'd love to hear the depth of your experience in cryogenic stress relief in metals. What kind of equipment did you use?? What metals did you employ in your experimentation??

    Are you aware of work done by other metallurgists in the field of cryogenic stress relief?? What were their findings?
     
  12. mete

    mete Member

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    Nero, my experience in stress relieving is years of doing it by HEATING. In any case lets take the statements of Cryoplus with my comments. 1-cryo will anneal the metal = annealing by definition is heating ( even my 1935 Funk &Wagnalls says that) 2-forms denser molecular structure = this is a pet peave of mine, metals do not have molecules nor do they have molecular bonding this is something you find in plastics. Metals have metallic bonding. 3- forms microfine carbides = this I think they took from a study about TOOL STEEL.The typical chrome moly barrel (such as 4140 ) is not tool steel and acts differently. Other comments that you might see about retained austenite also pertain to tool steels . All my comments require that you can deal with reason, logic and scientific fact.
     
  13. Badger Arms

    Badger Arms Member

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    Metals do have molecules and they have grains as well. The granular structure of the metal dictates much of what we know as the properties of hardness, brittleness, tensile strength, etc. Many of the alloying agents in metals are there to change the nature of the granular structure. Cryogenic treatment does something, but many argue over what exactly it does. One thing is for sure, it does stress-relieve metal. It also, from what I've experienced, makes tools last longer. This is particulary true of band saw blades. The same should also apply to barrels, but I'm not sure if many users would experience any advantage from this over any other procedure (fire-lapping, 'break-in' procedures, recrowning, etc.).

    My personal opinion, if you have the money and it makes you feel better, it won't hurt and will probably help. Don't expect miracles.

    BTW, Mete, it doesn't form a denser molecular structure, but it does relieve intergranular stress.
     
  14. mete

    mete Member

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    Badger, please do some research in basic chemistry and learn about the different types of bonding, If you do you will find that metals do not have molecules.The type of bonding gives metals their properties as apposed to those of plastics. The basic reason for cryogenic treatment is to reduce the amount of retained austenite in the steel. This is a factor only in steels of fairly high carbon ( ~ 1% ) and significant amounts of other alloying elements, that is tool steels. That would include band saw blades. In practical experience it helps in some cases but not others, you have to try it. And in some cases such as case hardened bearing some retained austenite is beneficial. As far as stresses, residual stresses distort the crystal structure. This can be measured by X-rays. Atomic activity is higher at higher temperature and since you want those atoms to move , stress relieving is done by heating. This you can find in metallurgical texts, heat treating books. specifications etc.
     
  15. Badger Arms

    Badger Arms Member

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    Austenite is ferric carbide (a molecule within metals) which is an impurity among dozens of common impurities (molecules) within iron compounds such as steel, stainless steel, carbide steel, etc. Impurity might not be the best of terms because it does add certain benefitial properties to the steel. I'm not sure if I remember correctly from college, but I think that this is a stainless steel compound. Anybody? It seems you might be misunderstanding the use of terms here. Molecules are groups of atoms bound with electromagnetic forces. Some of these forces are quite strong such as the bond between Hydrogen and Oxygen within a water molecule. Others are comparatively weak such as the bond between two iron atoms in the molecular structure of steel.

    I doubt very seriously if cryogenic treatment does anything for the levels of any carbon compound in the steel. It is my understanding that cryogenic treatment merely reduces the volume of the steel significantly enough to rearrange the grains within the steel in a more uniform manner. When steel is formed, forged, cast, etc., it slowly cools. Irregularities in the cooling level within adjoining grains creates stresses in these areas. These stresses are relieved somewhat by further cooling the grain structure and squeezing these grains into a more uniform and less internally stressed structure. This is a factor in all steels, not just high-carbon steels.

    Finally, I've not seen any evidence that this is significant enough to warrant spending the money on it, but the process does accomplish something. Arguing about the semantics won't help us. That said, I'm not really sure I understand what you mean by a 'molecular bond' and what significance that has to metalurgy. It seems that you are refering more to an adhesive term.
     
  16. mete

    mete Member

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    Badger, I am not misunderstanding terms and I don't want to argue ,only educate. Austenite is not ferric carbide, it is a face centered cubic crystal structure found in iron and iron alloys. Groups of crystals (not molecules) form grains. Impurities are unwanted elements in steel, desired ones are alloying elements. Austenite is the structure of austenitic stainless steel ( 300 series) The difference in types of bonding is very significant, for example metallic bonding gives you electrical conductivity in metals. Stress relief HEAT treatment is normally done between 900-1250 F this permits atoms to move and relieve stresses.
     
  17. George Stringer

    George Stringer Member

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    I'm not a metalurgist and I don't know from atomic molecules. But it sounds like you are both right and just using different terms to express it. Tempering hardened steel is done by heat. Stress relief is simply tempering in that light. On the other hand Cryo does do something. Cryo, I think you are both saying, is a shot in the dark. From my experience with it that is absolutely correct. I may have sent several barrels to be treated for customers. Out of those I'd say 2/3 of them reported improvement and the rest except for one saw no change in accuracy. The one guy said his groups actually got bigger after treatment.

    I think this could be a very interesting discussion. You might cite some references for those interested to look up. The following is a quote from One Cryo www.onecryo.com

    "A One-Time Permanent Process Which is Not a Coating and Will Not Wear Off. Cryo Stabilizing Increases Dimensional Stability, and Accuracy of your gun barrel 15 to 30%. Reduces Wear, Friction, Heat and Warping, Resulting In Consistently Tighter Shot Groups. Cryo Stabilizing Closes and Refines Grain Structure of Ferrous Metals, Stress Relieves Aluminum and Other Non-Ferrous Alloys For Tighter Tolerance Machining"

    Make sense? George
     
  18. mete

    mete Member

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    No George. Their website has a good bit of misinformation like the others. Least you think that stresses in barrels is something new , there is an excellent discussion of the subject in " The Modern Gunsmith " by Howe, 1941 edition, Supplement page 21. Maybe we should leave it there, if $50 makes you happy it's cheaper than going to a shrink.
     
  19. Wildalaska

    Wildalaska member

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    We have had nothing with sucess from cryo..I dont pretend to know how it works...but it does....
     
  20. JollyWhiteGiant

    JollyWhiteGiant Member

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    If you are planning on fluting a standard or HBAR conture barrel, save yoru money as it woun't reduce weight enough to really notice. If you are getting a bull barreled rifle it can save you quite a bit of weight depending on who does it and how deep they go with it.

    It may help cool bull barrels quicker but doesn't do much for HBAR barrels.

    Any shop that does fluting should releive their barrels after doing it. I too would stay away from Cryo, and only use it as a last resort if you can't get it to shoot and even if you get increased accuracy it will not be dramatic.
     
  21. Frohickey

    Frohickey Member

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    Please. Keep the metallurgy class/discussion going. Thats one of my interests, though I admit, I'm very much a layman at it, but its one of those things that I took a class in college, and have been fascinated with since.

    It might be, as far as cryo-ing and heat treating for stress relief, is that its the uniform cooling that is what is required. With heating, don't you lose some desired structures depending on how long it was heated?

    And for fluting and cooling of the barrel, sure, you increase the cooling effect, because you have just increased the surface area of the barrel. But a lighter barrel has less metal and tends to heat up faster than a heavier barrel. I think that its a wash as far as number of shots fired from a cold barrel to temperature.
     
    Last edited: Jan 3, 2003
  22. Nero Steptoe

    Nero Steptoe member

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    Mete: I have a college-age son...just wondering where you got your degree in metallurgy?? Your assertion that metal "doesn't have molecules" is the most bizarre statement I've heard from somebody professing to be a metallurgist. In other words, iron isn't made up of atoms that form molecules??

    Maybe I'm missing something here, but I'd hope that many complaints would have been filed with the Federal Trade Commission if the several companies that offer cryo treatment of metals just happen to all be frauds.

    As I said, have you done any research into work done by any PUBLISHED metallurgists regarding their work in cryo stress relief in metals??
     
  23. Delmar

    Delmar Member

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    Well, so far as it goes-if you want to increase the surface of the barrel in order to affect cooling, glass beading the exterior is going to give you more surface than fluting.
     
  24. mete

    mete Member

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    Nero, Polytechnic Institute of Brooklyn ( now Polytechnic University). I'll try it again. In metals groups of atoms form crystals not molecules. This is bizare only if you don't know science. Austenite -face centered cubic crystal, ferrite- body centered cubic crystal, martensite- tetragonal, these are the three CRYSTAL structures ( NOT MOLECULES) that we deal with in iron alloys. If you can't even get to square #1 I can't help you.
     
  25. romulus

    romulus Member

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    No offense, but I find the statement bizarre also...Mete, does it hold true only for metals that crystals have no molecular structure? Diamonds and other crystalline gems have a molecular structure. What is it about metals, that the atoms would somehow refuse to bond and form molecules?

    Also, as I understand it the definition of "annealing" is the softening of metal...does it have to be done by heating? If cryo-handling of steel results in a softer metal, why is it not annealing? Could you kindly refer me to a text other than Funk and Wagnall that might shed light on the subject?

    Just curious...
     
    Last edited: Jan 3, 2003
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