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Thread: Some notes on HPT/MPI

  1. #21
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    Quote Originally Posted by 5pins View Post
    BCM seems to be straight forward about what they do.


    The term milspec is meaningless. Go to any gun show and everything you see will be milspec. It’s become to broadly used to sell stuff from people that don’t understand what it means to people who don’t understand what it means.

    I also went to the Daniel Defense sight and notice that they make no claim to HP test, just MPI.
    I agree,the term mil-spec is a generic term that is abused throughout the market on just about everything from ammo,gear and weapons.

    As far as DD's BCG technical specs...Ive called and emailed several times to inquire about the specs of the BCG's,the only real response I got was from Joe Marler at DD in this thread:
    http://www.ar15.com/forums/topic.htm...f=382&t=185718

    HPT and MPI or not,do I feel the DD BCG's are quality,well in my sample size of two I'd have to say yes in the limited amount of time Ive had to put them to use.The manufacturing/machining of the components used in the BCG's is certainly very well done per eye ball and touch.
    Other than that I will have to take DD at their word on the claims.
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  2. #22
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    I've emailed DD twice and haven't heard back. Bravo Co always responds with a great attitude, even if I tell them don't bother, as I found the product or info etc...

    DDs verbage in bbl description is odd, using the term "MP Tested".

  3. #23
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    The markings on my DD M4 barrel says “DD 4150 MP 5.56 NATO 1/7”. I have a DD lightweight coming next week and I will see what it says.

    I don’t think that the fact that a manufacture is not doing HPT/MPI should an indicator that that their products are substandard. However If the rejection rate is 3%, does that mean that there is a lot of rifles out there not making Gov. standard?

    How many companies are doing HPT/MPI anyway? Colt, FN, BCM… those are the only ones I can think of off the top of my head.

    Here is a youtube video on Magnetic Particle Inspection that explains the process.

    http://www.youtube.com/watch?v=4P3DzZzXwa8

  4. #24
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    Quote Originally Posted by 5pins View Post
    The markings on my DD M4 barrel says “DD 4150 MP 5.56 NATO 1/7”. I have a DD lightweight coming next week and I will see what it says.

    I don’t think that the fact that a manufacture is not doing HPT/MPI should an indicator that that their products are substandard. However If the rejection rate is 3%, does that mean that there is a lot of rifles out there not making Gov. standard?

    How many companies are doing HPT/MPI anyway? Colt, FN, BCM… those are the only ones I can think of off the top of my head.

    Here is a youtube video on Magnetic Particle Inspection that explains the process.

    http://www.youtube.com/watch?v=4P3DzZzXwa8
    I agree,I care more about the materials used and how well the work was performed in the manufacturing and treating process.HPT and MPI be damned if the part is made out of substandard materials and manufactured poorly.
    Some folks bash DD for not marking the bolts MP,I could careless what letters are stamped or engraved on the part if it comes from a company I have confidence in quality.As someone mentioned before its easy to stamp or engrave MP etc. on a bolt,just because its there does not make it so and does not indicate HPT was actually performed before hand.
    I do think a lot number or code would be good to use on the bolts in the case that there is a string of failures which would ease tracking the issue to a specific production run rather than a blanket type failure call out if it ever does occure.
    For Example Armalite marks all the bolts with a letter/digit lot#,LMT uses a letter lot code.
    As someone who works in the trouble shooting and warranty/recall/repair related business(motorcycle industry),I think that is a responsible way of doing things.
    Ive also read that a scribe or engraved type marking is much better to use on heat treated parts like a bolt rather than hammer stamp type markings.

    As far as manufacturers that do HPT/MPI,you can add LMT to that list.
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  5. #25
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    Quote Originally Posted by Blankwaffe View Post
    HPT and MPI or not,do I feel the DD BCG's are quality,well in my sample size of two I'd have to say yes in the limited amount of time Ive had to put them to use.The manufacturing/machining of the components used in the BCG's is certainly very well done per eye ball and touch.
    Other than that I will have to take DD at their word on the claims.
    I believe he was referring to the barrels.

  6. #26
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    Quote Originally Posted by Blankwaffe View Post
    I agree,I care more about the materials used and how well the work was performed in the manufacturing and treating process.HPT and MPI be damned if the part is made out of substandard materials and manufactured poorly.
    Funny thing about that....

    As it has been explained to me, barrels made of a lesser material than the 11595-E that is spec'd for barrels may have trouble making it through the HPT/MPI process (meaning passing the test, not that it's going to explode or something ).

    I do think that it might be entirely possible to make a barrel of equal life and accuracy from alternative materials, with alternative coatings and finishes, and that is tested in ways other than the military specification calls for.

    Additionally, when was the last time you heard about even a 4140 barrel failing? Outside of a squib or other barrel obstruction situation, of course.

    Everyone has to make up their own mind as to what works for them and what materials and testing they prefer to see on their parts. The purpose of this thread isn't to talk up or talk down any one brand vs. another but is to try and give people as much information as possible, as well as showing them where that information came from and where they can go to get more. some just aren't going to be that interesting. I sent a friend a link to this thread when I started it and he wrote back with "I don't really give a shit, I just buy Colts". Hard to argue with that. But at least he made a choice. I think there are a lot of people out there that would like to know more they just don't know where to find it. Hopefully this thread helps a little.
    Last edited by rob_s; 03-31-10 at 06:59.

  7. #27
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    The only barrel failure that I know of is here. Technically it was the barrel extension that failed but the point is that it looks like substandard parts. It looks like a casting to me. Bolt failures seem to be more common, at least some people recommend having a spare bolt.

    Some may question the need for HPT/MPI. How many other firearms designs is this done to? I read some place that Beretta does it to the locking blocks on the M9, and Sig on the M11 slide.

    One more thing. What about just MPI only? Is MPI with out HPT viable? Or is false since of quality assurance.

  8. #28
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    Quote Originally Posted by 5pins View Post
    One more thing. What about just MPI only? Is MPI with out HPT viable? Or is false since of quality assurance.
    I have somewhat changed my mind on this, however knowing the rejection criteria makes all the difference in the world. I don't think that MPI without HPT is as good as doing both, but if the rejection criteria for MPI includes more than just any and all cracks then I think it may have some merit.

  9. #29
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    Quote Originally Posted by rob_s View Post
    I believe he was referring to the barrels.
    Oh,got it.
    Here is info from Joe in regards to barrels markings:
    http://www.ar15.com/forums/topic.htm...f=382&t=187489
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  10. #30
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    Quote Originally Posted by C4IGrant View Post
    From conversations I have had with various companies, I would say that they failure rate is around 3%.
    C4
    I'm curious what round count you would peg the 3% failure rate to occur by. I'm pretty confident that over 95% of all AR's out there now haven't seen round #1001 yet (all but one of mine included, sadly), and I'm assuming the types of failures that would be highlighted and caught early by HPT/MPI testing would increase drastically as the round count got over 5k, and catastrophic failures (I'm assuming bolt lug or separation at the cam pin hole).
    The discussion on this really should be an academic one, but it's the internet, and we're cheap: fact remains that to see wear related failures on rifles it usually costs at least the original cost of the rifle in ammunition to really expect part failures, which among the population of completed ARs is the exception, not the rule.
    Virtually anybody with the experience to budget their rifle AND the rounds they expect for it to see immediately realize the false economy of cheap barrels and BCG's, and just go exclusively with stuff from the half dozen top end manufacturers.

    What makes me the most curious is how many original sources there are for bolts. CMT as far as I know makes a large amount of them, and they get used by lots of other companies (but emerge in many unique flavors - cheap, MPI tested alone, HPT/MPI).
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