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Thread: Bolt life question.

  1. #91
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    Quote Originally Posted by Heavy Metal View Post
    Bill,

    The reason Grumpy is so intent on this line of questioning, is he had his HK- MR556 bolt QPQ'd a couple months ago before you made your post yesterday. He is kind of stuck with the results at thsi point.
    Exactly.

    Some of the stuff Bill has been talking about wasn't something that I could find anywhere, regardless of the countless hours I spent researching nitriding prior to having the process done.

    Much of it I did find though, and unfortunatly, most of it, just like Bill himself has said, is a whole lotta "maybes", "mights", "mays", etc. without any hard data, especially end user data or real test data to back it up.

    Not poo-pooing what Bill is saying as he has a very firm grasp on the technicals and possibilities, but at the same time, we're once again left in a position where we're lacking empiracle data.


    Quote Originally Posted by E-man930 View Post
    Now that's funny!
    Looks like someone jumped both feet in before understanding the complexity of their decision.
    I did exactly, that. But to be honest, I'm not too worried about it. The "complexity" of the decision is still left in theory mode as there is no data. I think Constructor would have a better idea of this as he actually sells Nitrided DI bolts and would be in a position to hear enduser feedback if those bolts were demonstrating markedly shorter lifespans then typical DI bolts.

    I suppose the questions at that point are: How long has Constructor been selling nitrided bolts for?, Have any customers given positive feedback regarding high round count rifles?, and has he done any testing of his own on his product?


    Look, i'm all for trying to understand everything one can about a process before arbitrarily just having it done without thought to possible side effects. I did all the research I could and there was not a lot about this exact topic. So I took the plunge.

    At the same time, the information we've gotten on this exact topic from Bill, has been.....less then revealing. Lots of maybes that ultimatly result in "I don't know"s. It's one thing to explain the theory, it's another to have the data. So far, all we have is theory.

    If my parts break and don't last, well then i'll be a part of that data and can help someone else in the future. No skin off my back. It's just a bolt.
    It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori

  2. #92
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    Quote Originally Posted by Bill Alexander View Post
    Let me clarify for you Bill.
    We had 2 Grendel bolts break because the receiver the Grendel barrel was in was not square. Do you square your receivers Bill?
    After we squared the receiver for the Grendel customer he has not broken another bolt. Just never know when a smile is going to bite you in the ass do you?

    BTW we may start making Grendel bolts, we have only made 264LBC bolts for the last few years.
    Last edited by constructor; 06-12-12 at 00:48.
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  3. #93
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    Quote Originally Posted by GrumpyM4 View Post
    Exactly.

    Some of the stuff Bill has been talking about wasn't something that I could find anywhere, regardless of the countless hours I spent researching nitriding prior to having the process done.

    Much of it I did find though, and unfortunatly, most of it, just like Bill himself has said, is a whole lotta "maybes", "mights", "mays", etc. without any hard data, especially end user data or real test data to back it up.

    Not poo-pooing what Bill is saying as he has a very firm grasp on the technicals and possibilities, but at the same time, we're once again left in a position where we're lacking empiracle data.




    I did exactly, that. But to be honest, I'm not too worried about it. The "complexity" of the decision is still left in theory mode as there is no data. I think Constructor would have a better idea of this as he actually sells Nitrided DI bolts and would be in a position to hear enduser feedback if those bolts were demonstrating markedly shorter lifespans then typical DI bolts.

    I suppose the questions at that point are: How long has Constructor been selling nitrided bolts for?, Have any customers given positive feedback regarding high round count rifles?, and has he done any testing of his own on his product?


    Look, i'm all for trying to understand everything one can about a process before arbitrarily just having it done without thought to possible side effects. I did all the research I could and there was not a lot about this exact topic. So I took the plunge.

    At the same time, the information we've gotten on this exact topic from Bill, has been.....less then revealing. Lots of maybes that ultimatly result in "I don't know"s. It's one thing to explain the theory, it's another to have the data. So far, all we have is theory.

    If my parts break and don't last, well then i'll be a part of that data and can help someone else in the future. No skin off my back. It's just a bolt.
    Our bolts aren't like most other bolts and I'm not going to post everything I changed on an open forum but it seems like the HK bolt has a few of the same features. Anyone that has one of our bolts can compare it to a mil spec bolt and easily see the changes and should be able to understand the whys. The extra amount of material itself will change the lifespan more than anything if the alloy and heat treat are the same. IMO QPQ does make the surface more corrosion resistant which may slow or prevent the pitting that can be the starting point of stress cracks. QPQ actually softens an already carburized bolt but maybe only 1 point according the the engineer at the plant and 1 point changes the TS or YS very little.
    I have never heard of any company doing a test to see how QPQ effects the life of a bolt. From what Burlington told me I can't see it hurting the bolt.
    I only tried one batch of apx 280 bolts 3 years ago, all of them were 6.8 bolts so I doubt the round counts on those are very high.
    None of the QPQ, TiN or TiAlN coated bolts have been reported broken.

    ETA- the only tests I have done were shear strength tests at the lugs. A fixture with the same dia as a barrel extension but solid, bolt under pressure from the recess area same as a cartridge would do. LWRC back when it was Leitner Wise was already using 9310, I had 4 of those 6.8 bolts. I shot a charity 3 gun event in Durango with the 6.8 using a LWRC bolt and ammo loaded with 90gr TNTs as hot as I could load them without blowing primers. 32.5gr of 10X with SSA brass and CCI 41 primers doing just over 3100fps from an 18" barrel. Round count was 170 minimum and I fired a few extra. I think I still have that bolt in a rifle. I believe those loads to be in excess of 65000psi but not near the Hornady 70,000psi proof loads I test bolts with(1 shot only)
    Last edited by constructor; 06-12-12 at 01:06.
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  4. #94
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    GrumpyM4 my exasperation was not directed towards you. Your questions are reasonable and well phrased.

    It would appear that drilling a few holes in barrels trumps a metrology lab and years of experience, I will let the US Army and the few defense contractors I consult to know, so that they can dump all that expensive, but obviously ridiculous, equipment and the staff.

    Equally it would appear that fatigue can be analyzed by firing a few overloaded rounds. And there I was thinking that we needed to run pressure equipment to calibrated standards and resonant load machines to examine fatigue.

    The error in this thread lies with myself. I was foolish enough to think that a reasonable contribution might be of help. Instead I find that I am being drawn into a squabble more appropriate to TOS, which has more basis in points scoring that factual information. My absence from this forum will commence.

  5. #95
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    Bill, I really appreciate your input and contribution to this forum (not to mention this thread in particular)!
    Last edited by skullworks; 06-12-12 at 12:23.

  6. #96
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    Quote Originally Posted by Bill Alexander View Post
    GrumpyM4 my exasperation was not directed towards you. Your questions are reasonable and well phrased.

    It would appear that drilling a few holes in barrels trumps a metrology lab and years of experience, I will let the US Army and the few defense contractors I consult to know, so that they can dump all that expensive, but obviously ridiculous, equipment and the staff.

    Equally it would appear that fatigue can be analyzed by firing a few overloaded rounds. And there I was thinking that we needed to run pressure equipment to calibrated standards and resonant load machines to examine fatigue.

    The error in this thread lies with myself. I was foolish enough to think that a reasonable contribution might be of help. Instead I find that I am being drawn into a squabble more appropriate to TOS, which has more basis in points scoring that factual information. My absence from this forum will commence.
    So are you saying that the 9310 alloy that LWRC, JP, LMT, Myself and even that you have said in the past that you have your bolts made from is not strong enough for use as bolts in a AR15? Or are you saying the larger radii and more material due to design changes that HK and I have made make the bolts weaker?
    The only thing I said was from what I have seen the hundreds of melonite barrels I drill through are a hell of a lot softer on the inside than a 9310 alloy bolt that has been carburized.
    The engineers at the companies that actually perform the melonite process told me I would not get the desired results by ONLY melonite treating a 9310 bolt. That is why I have the bolts carburized first and then do what ever treatment after.
    So when is the military changing to melonite treated bolts?
    AR15performance
    TRUMP 2020
    The 6.8 is the best choice for hunting deer and hogs with an AR15.

  7. #97
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    Quote Originally Posted by skullworks View Post
    Bill, I really appreciate your input and contribution to this forum (not to mention this thread in particular)!
    I agree as well, Bill has made some excellent contributions.

  8. #98
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    Same here. Your contribution was meaningful, and a lot of us clearly do appreciate it, even if not actively posting in this thread.

  9. #99
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    I just come here for the information. Don't want to start fights.
    It is missing the point to think that the martial art is solely in cutting a man down; it is in killing evil. It is in the strategem of killing the evil of one man and giving life to ten thousand -Yagyu Munemori

  10. #100
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    Ok, I got some information regarding wear on the HK bolts in our guns, from the head armorer in the NDLO.

    Initially, there were some issues with bolt lugs shearing after a low round count, on some of the first weapons issued.

    This was a result of HK changing their steel supplier, and this supplier had some issues with the alloys used and the hardening process. They switched back to the original supplier, and these issues went away.

    The warranty on parts life that we have from HK is 10000 rounds, with regards to service intervals. The warranty we have from Colt Canada on the C8's is 6000 rounds.

    What they have seen, as far as bolt lugs shearing off, is that it happens on some weapons, depending on firing schedules, after 8-10k rounds. For them, that is acceptable, and they just replace the parts without any more fuss.

    I will also concede that I was in error with regards to the unlocking process, and that the unlocking in the DI design is less stressful than the op-rod design, seeing as the op-rod strike is instantaneous, and not gradual.
    Last edited by Arctic1; 06-15-12 at 03:44.

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