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Thread: Why is 4150 steel better?

  1. #11
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    I'm also speaking off-line with a bench-rest shooter, who also builds AR-15 rifles, and he seems to think that the additional hardness helps with the rate at which the muzzle "bells out" as higher round counts/rates of round counts increases. This is more prominent with threaded barrels than unthreaded barrels, btw.

    That appears to make sense on the surface.

    I know from working on aviation steels, that it is much tougher to screw up the lower numbered steels. 4130 is the easiest to work on, while 4140 and 4150 become harder to work without making them overly brittle or wearing out your tools. In other words, if you don't have perfect quality control, 4140 has a better chance of turning out "tougher" than 4150. The additional hardness potential of 4150 requires a higher QC, in other words.

    I seem to recall something about heat dissipation superiority of 4150 over 4140.

  2. #12
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    Quote Originally Posted by GONIF View Post
    So the" I think" test is your hall mark test ? maybe someone should tell Colt,Bushmaster,and LMT they are wasteing money . the big guys pay so little for the upgraded steel it is a non issue . some folks need ,want,deserve and get the best some don't. I for one a'm not going to tell anyone what is good enough for them ,I deserve the best and that ain't good enough . life is short why settle ? Cheap scotch will get you drunk just as fast as12 year old Single Malt will ,but it won't make you smile after each sip . I realy a'm not trying to bust you chops ,but best is best and for most of the things we buy it may be a moot point an AR is in fact a weapon you may some day have to bet your life on so get the real deal proven to be superior barrel .just MHO. YMMV
    I wrote "I think" because I am 1) admitting that, not being an expert in some things such as metallurgy, I must rely on the expertise of others, and 2) although I have never once found any barrel failure in civilian usage of 4140 v. 4150, there may be a case of it happening. I still have not heard of such a failure, nor have you provided any such information.

    Your response contains its own "I think" on your part. You "think" the military is using the very best steel out there for its barrels. Do you know that for a fact? Although the military has performed numerous and expensive studies of various materials, every decision is a compromise. One need only look at the history behind the M-16's development within the military to see that. Based on my experience in the military, which includes 2000 flight hours with the Navy, I can assure you that there are other times when the military makes compromises. For example, my issued MB-4 flight computer (a type of aviation slide rule for solving navigational problems) had letters and numbers painted on the metal surfaces. Those letters and numbers soon wore off, so I (like every other nav I worked with) bought a civilian version in which the letters and numbers were etched into the surface. The military version was a compromise. The civilian version was a compromise. In my case, the civilian compromise was the better of the two.

    Based on my experience in the military, my experience in production management, and my common sense, I believe the military is using the best compromise for its purposes when it demands 4150 steel for its barrels. I also believe that there is probably an absolute best, no-compromise steel for military purposes that the military would not choose because it would be far more expensive than the 4150 that sufficiently does the job. I also believe that the military's purposes do not perfectly mirror civilian purposes, and that the differences warrant thoughtful consideration rather than blind adherence.

    Your scotch analogy is flawed because it compares two vastly unequal choices. A better analogy is the difference between Napa Valley wines and Sonoma County wines. Each region produces high-quality, flavorful products, but they satisfy different flavor expectations for the drinker.

    But back to the point: If you have any proof that my 4140 barrel is going to fail in my time of need simply because it's not 4150 steel, please provide that proof. Otherwise, you're preferring 4150 simply because "you think" it's better for civilian usage.

    P.S. If you think the big guys (or anyone else) will pay even a little bit more for their steel but not pass that additional cost along to consumers, so that it becomes a non-issue, then you and I will have to agree to disagree.
    Last edited by Whytep38; 09-02-07 at 11:01. Reason: P.S. Added.

  3. #13
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    It was explained to me by someone with a PEng in something relating to this - that the metal maintained its strength better when hot. Creating a safer barrel - and one with a greater longevity.
    It was in relation to accessory mounting and the like - so I cannot offer anything else other than it will droop less etc.
    *I'm a knuckledragger so take this with a grain of salt, all of the conversation was in relation to the droop and subsequnt bolt sheer when weight is applied onto the barrel...
    Last edited by KevinB; 09-02-07 at 10:50.
    Kevin S. Boland
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  4. #14
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    Quote Originally Posted by KevinB View Post
    It was explained to me by someone with a PEng in something relating to this - that the metal maintained its strength better when hot. Creating a safer barrel - and one with a greater longevity.
    It was in relation to accessory mounting and the like - so I cannot offer anything else other than it will droop less etc.
    *I'm a knuckledragger so take this with a grain of salt, all of the conversation was in relation to the droop and subsequnt bolt sheer when weight is applied onto the barrel...
    Kevin,

    Given that it's "heat related", did your PEng indicate whether or not semi-auto fire would be enough to stress the steel and get to the heat threshold where 4150 makes a difference? I've heard the arguments that 4150 is needed only for FA fire, just wondering if that statement has any merit or if there's a known rate of fire where 4140 enters the not so desirable" zone.

  5. #15
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    Well it was in relation to 4150 versus other compositions.
    And the forces and heat when items like a rail, grip, PEQ and light are added.
    It was a military related issue - so the modelling and testing involved a high rate of fire.

    I was more hoping someone with some metalurgical background would chime in.
    Kevin S. Boland
    Manager, Federal Sales
    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
    www.fnhusa.com

  6. #16
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    Note should be made that the steel quoted by the OP was 4150 CMV An examination of the chemical analysis of 4150 per AISI specifications shows that this steel is indeed an easier hardening grade but also that vanadium is not present in the alloy. The confusion in terms of barrel steel is that the correct alloy is not 4150 rather a modified vanadium bearing grade per mil specification. The presence of vanadium acts to slow the response of the steel to heat treatment but also as a grain refiner. This promotes excellent ductilty and a high Kic value.

    With this noted buyers should beware that they are not getting what they believe is a premuim barrel steel when in fact the vendor has simply used plain AISI 4150 in place of 4140.

    Bill Alexander

  7. #17
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    This subject always get's heated,and never has a answer everyone is happy with. IMHO no one can afford to do the extensive testing that our Gov has done on this subject and as such I will defer to them on this. I have had first hand experience with both and have not had a failure with ether. my research on this subject has led me to belive the 4150 is superior for a chrome lined AR15/M16 barrel . as far as believeing our government ,I can't help you there .you aren't even going to get me started on that . life is strange,just the other day I saw on TV news that mother Taresa (spelling) lost her faith at some point B4 she died . kinda makes you wonder how she came to that .
    WHO ME ? ---- A government big enough to
    give you everything you want, is
    strong enough to take everything
    you have.
    -- Thomas Jefferson

  8. #18
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    Quote Originally Posted by Bill Alexander View Post
    Note should be made that the steel quoted by the OP was 4150 CMV An examination of the chemical analysis of 4150 per AISI specifications shows that this steel is indeed an easier hardening grade but also that vanadium is not present in the alloy. The confusion in terms of barrel steel is that the correct alloy is not 4150 rather a modified vanadium bearing grade per mil specification. The presence of vanadium acts to slow the response of the steel to heat treatment but also as a grain refiner. This promotes excellent ductilty and a high Kic value.

    With this noted buyers should beware that they are not getting what they believe is a premuim barrel steel when in fact the vendor has simply used plain AISI 4150 in place of 4140.

    Bill Alexander
    Thanks Bill I was hoping you would chime in on this one.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  9. #19
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    Even with the information provided by Bill, I don't see an easy answer to the OP's question about why 4150 is better. The answer isn't easy because you must consider the entire context. The government's testing was performed with specific military, not civilian, criteria in mind. To say "best is best" without taking into account any other considerations is an over-simplification.

    I don't know which of the weapons listed below does or does not use modified vanadium 4150 barrel steel, but I suspect at least one does not:

    M1
    AK-47
    M2
    Abrahms tank

    Using the simple "best is best" approach, if any of the above weapons use something other than modified vanadium 4150, they would not be using the best barrel steel. Thus, anyone betting his life on such a weapon would not get the real deal. And yet I've never heard of any of the above weapons being faulted for their barrel steel. I suspect that's because the "best is best" approach is so highly dependent on so many factors that there is no universal "best is best" for all applications.

    If people feel better about choosing 4150 (whether modified vanadium or not) over 4140, that's their choice. One should choose what best fits one's comfort zone. But scare-mongering folks about the issue without any proof is a different thing.

  10. #20
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    Quote Originally Posted by Whytep38 View Post


    If people feel better about choosing 4150 (whether modified vanadium or not) over 4140, that's their choice. One should choose what best fits one's comfort zone. But scare-mongering folks about the issue without any proof is a different thing.
    Who's scare-mongering here?

    I think there's VERY little statistical difference too. For the people that shoot 500 or less rounds a year the difference is nill.

    Last month I shot over 500 rounds through my 3gun rifle, and 2 others (400 though my LMT and 100 through my Colt) and that was a fairly light month.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

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