Page 5 of 6 FirstFirst ... 3456 LastLast
Results 41 to 50 of 52

Thread: Some notes on HPT/MPI

  1. #41
    Join Date
    Feb 2009
    Location
    SC
    Posts
    505
    Feedback Score
    1 (100%)
    Quote Originally Posted by sniperfrog View Post
    I've seen a shit ton of rounds go through Colt M4s. I've worn the barrel out of one in about 3 weeks. Yet I had never heard of a Colt bolt breaking. I never new broken bolts were a problem until I had to carry a BM.

    I've had to replace 3 at my unit in the last 6 months. Granted it was after quarterly training exercises where thousands of rounds have gone through the guns. And like Redhat posted, it was the lugs next to the extractor. One even had a crack moving to the next lug over from the broken one.
    Last edited by R/Tdrvr; 04-02-10 at 09:07.
    Failure to train is training to fail.

  2. #42
    Join Date
    Jun 2006
    Location
    Niantic CT
    Posts
    1,964
    Feedback Score
    6 (100%)
    How long has HPT/MPI been required? Have they been doing it from the beginning when Armalite develop the AR10, or did they start doing it later because of problems?

  3. #43
    Join Date
    Dec 2006
    Posts
    346
    Feedback Score
    0
    Quote Originally Posted by R/Tdrvr View Post
    I've had to replace 3 at my unit in the last 6 months. Granted it was after quarterly training exercises where thousands of rounds have gone through the guns. And like Redhat posted, it was the lugs next to the extractor. One even had a crack moving to the next lug over from the broken one.
    The last time I put serious rounds through the Colt M4 was back in the '90s. My Team went through alot rounds during training. I don't know why we never had broken bolts but I really can never remember that being an issue. I've done training where we were putting 800-1000 rounds a day through each gun for a couple weeks. The armorer checked our barrels after and they were completely wore out, yet out of about 20 of us, no one broke a bolt.

    With the BMs, I've mostly seen bolts break at the cam pin hole.
    Last edited by sniperfrog; 04-02-10 at 15:38.

  4. #44
    Join Date
    Jul 2006
    Location
    Midwest, USA
    Posts
    8,194
    Feedback Score
    1 (100%)
    Quote Originally Posted by sniperfrog View Post
    I've seen a shit ton of rounds go through Colt M4s. I've worn the barrel out of one in about 3 weeks. Yet I had never heard of a Colt bolt breaking. I never new broken bolts were a problem until I had to carry a BM.
    Colt bolts do indeed break. I've seen several, and others have discussed them online. They break at the lugs though, and after a good service life, unlike others that may do so at the cam pin hole and at any time.
    2012 National Zumba Endurance Champion
    الدهون القاع الفتيات لك جعل العالم هزاز جولة الذهاب

  5. #45
    Join Date
    Nov 2008
    Location
    NM
    Posts
    3,988
    Feedback Score
    10 (100%)
    The bolt only needs to last as long as the barrel (anything else is a parts and maintenance issue). I'm pretty confident the bolts that will fail HPT/MPI testing won't meet this, so that's my target - is this logical?
    عندما تصبح الأسلحة محظورة, قد يملكون حظرون عندهم فقط
    کله چی سلاح منع شوی دی، یوازي غلوونکۍ یی به درلود
    Semper Fi
    "Being able to do the basics, on demand, takes practice. " - Sinister

  6. #46
    Quote Originally Posted by Luke_Y View Post
    Ahh... Yes, I see that now

    On one hand I look at HP/MPI as a procedure that finds the parts that are flawed from the get go. But, that HP is the key. If one never suffered an overpressure condition in their rifle I expect that a number of that 3% would likely serve through their normal expected service life without failure.

    Then, you have to figure that a certain number of that 3% would "fail" a MPI inspection at some point but not in a way that was user detectable or catastrophic, and may still serve out their expected service life or at least not be drastically reduced.

    Then, some part of that 3% would fail early, detectably, even catastrophically. Those are the ones I don’t want .

    Yes, it would be interesting to know the details of the 3%. How many are catastrophic failures? How many are detectable after the HP without the MPI? Stuff like that. Even more interesting and I suppose more to the point of what TehLlama was getting at would be to take a significant number that "failed" HP/MPI testing, but only in a way that was detectable with MPI, stick them in guns and see when they failed in an obvious/detectable manner.
    The failure rate estimate of 3% is for independently certified Mil-B-11595E barrel steel. If using commercial 4150/4150mod/CMV/etc and also using the acceptance/rejection criteria for the milpsec, the failure rate is closer to 30%. That does NOT mean your 4150/4150MOD/CMV/etc commercial barrel steel gun is ready to blow up or is unsafe. (please read that line again)
    It means that when using the very restrictive criteria for pass/fail (MP Inspection) that Uncle Sam requires, the barrel is not ok on a military gun.

    The overwelming majority of MPI failures under the mil standard of acceptance/rejection criteria have to do with inclusions in the barrel steel. (not catastrophic cracks, etc)
    .


    For the Worlds Best Gunfighter Training
    Please visit http://www.bravocompanymfg.com/gunfighters





    www.BravoCompanyUSA.com


    www.BravoCompanyMFG.com


    1 - 877 - BRAVO CO

    Semper Fi !

  7. #47
    On another note, every bolt will eventually fail and break at some point, whether its made from 4140, 8620, 9310 or Carpenter 158® steel. It's just better when they fail less often.

    The idea is that if the bolt is machined from Carpenter 158® steel, heat treated per RI print, shot peened per RI print, high pressure tested, and MPI inspected, etc. - the bolt should not fail nearly as soon (on average), as a bolt that does not include the above features. That is the goal and consensus of the US government engineers. It may or may not be applicable to your personal situation.
    Last edited by BravoCompanyUSA; 04-03-10 at 17:05.
    .


    For the Worlds Best Gunfighter Training
    Please visit http://www.bravocompanymfg.com/gunfighters





    www.BravoCompanyUSA.com


    www.BravoCompanyMFG.com


    1 - 877 - BRAVO CO

    Semper Fi !

  8. #48
    Join Date
    Jun 2006
    Location
    Niantic CT
    Posts
    1,964
    Feedback Score
    6 (100%)
    Quote Originally Posted by BravoCompanyUSA View Post
    The overwelming majority of MPI failures under the mil standard of acceptance/rejection criteria have to do with inclusions in the barrel steel. (not catastrophic cracks, etc)
    When you say “inclusions” are you talking about imperfections in the metal from the manufacturing of the steel?

    If so, then MPI with out HPT sounds like it would be useful because it would help weed out parts with manufacturing defects. I’m assuming that the HPT would not reveal inclusions that would not have been found otherwise.

    It would be interesting to see how many parts would pass inspection before HPT only to fail afterword.

  9. #49
    Join Date
    May 2008
    Posts
    395
    Feedback Score
    13 (100%)
    Quote Originally Posted by BravoCompanyUSA View Post
    The failure rate estimate of 3% is for independently certified Mil-B-11595E barrel steel. If using commercial 4150/4150mod/CMV/etc and also using the acceptance/rejection criteria for the milpsec, the failure rate is closer to 30%. That does NOT mean your 4150/4150MOD/CMV/etc commercial barrel steel gun is ready to blow up or is unsafe. (please read that line again)
    It means that when using the very restrictive criteria for pass/fail (MP Inspection) that Uncle Sam requires, the barrel is not ok on a military gun.

    The overwelming majority of MPI failures under the mil standard of acceptance/rejection criteria have to do with inclusions in the barrel steel. (not catastrophic cracks, etc)
    Quote Originally Posted by BravoCompanyUSA View Post
    On another note, every bolt will eventually fail and break at some point, whether its made from 4140, 8620, 9310 or Carpenter 158® steel. It's just better when they fail less often.

    The idea is that if the bolt is machined from Carpenter 158® steel, heat treated per RI print, shot peened per RI print, high pressure tested, and MPI inspected, etc. - the bolt should not fail nearly as soon (on average), as a bolt that does not include the above features. That is the goal and consensus of the US government engineers. It may or may not be applicable to your personal situation.
    Thanks for the insight, and your participation is appreciated.

    My curiosity mostly surrounds bolts and for some reason I was thinking that the stated failure rate applied to them. Do mil spec bolts have about the same 3% failure rate when HP/MPI tested? Do they fail in majority to inclusions as well, or are their failures more pronounced and obvious?

    My personal guns will never see the use/abuse that a military weapon is expected to withstand. For me HP/MPI on barrels is assurance that I am buying a quality product from a manufacture that cares. As well as a bit of insurance in the slight chance of an over-pressure condition caused by an undetected squib or bbl obstruction. I like to believe that the testing for pre existing flaws may lessen my chance of injury when the ka-boom happens.

    Bolts though are what concern me the most. Bolt breakage is a show stopper, and any insurance I can have against it in a duty or defensive carbine is good insurance.

    I know that some knowledgeable folk suggest that HP testing of bolts may slightly decrease its lifespan. But, if it greatly reduces the chance of an early catastrophic failure by weeding out the bad apples. And, the expected post testing lifespan is generally the same as the bbl then it's good by me. Like one of the other posters, I see no real reason for it to have an expected service life longer than the bbl.
    My fear is that ahh, the whole island will ahh, become so overly populated, that it will tip over and ahh, and capsize...
    Hank Johnson (D) GA YouTube

  10. #50
    Join Date
    Jun 2006
    Location
    SE FL
    Posts
    14,148
    Feedback Score
    5 (100%)
    Quote Originally Posted by 5pins View Post
    When you say “inclusions” are you talking about imperfections in the metal from the manufacturing of the steel?

    If so, then MPI with out HPT sounds like it would be useful because it would help weed out parts with manufacturing defects. I’m assuming that the HPT would not reveal inclusions that would not have been found otherwise.

    It would be interesting to see how many parts would pass inspection before HPT only to fail afterword.
    Remember, "MPI" is just a test that results in data. It's what you do with that data that matters.

    My GUESS is that the majority of makers who claim MPI, with or without HPT, are only rejecting cracks and not inclusions. As Bravo said, if you're not using 11595E you'll get a 30% rejection rate if you combine that with a PROPER rejection criteria. The cost savings of using 4150 would go right out the window.

    So what's a maker to do if they want more checkmarks? Make the barrel out of non-11595E 4150 steel, HPT (maybe), and MPI and only reject for cracks not for inclusions. Since the majority of rejections when doing it right are for inclusions and not cracks, your only increased overhead is in the testing not rejections. Remember that it you're rejecting 3% of your product you have to charge at least 3% more for it, where as a guy with zero rejections because he's using a lesser criteria doesn't have to charge that premium.

Page 5 of 6 FirstFirst ... 3456 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •