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Thread: Phosphate under gas block

  1. #111
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    Quote Originally Posted by lamarbrog View Post
    Not so much the method- the process entirely. If the bolt fits, and passes test firing- the dimensions are probably good. Something being dimensionally wrong with a bolt is so far down on the list of things I worry about...
    I don't feel comfortable that is enough. It may work in that gun, and still be out of spec - and may effect the longer term reliability statistics and/or may not work in another gun. That is the benefit of interchangeable parts. For example, a bolt which is out of headspace may still be within headspace as a complete rifle for a particular barrel, but I would still want to reject that bolt.

    Quote Originally Posted by lamarbrog View Post
    And I doubt LaRue does their own heat treating, too. But they likely contract it out to a reputable heat-treat facility, because they have a reputation for quality to uphold. Bushmaster and DPMS don't really have that same reputation.
    Let me tell you a story about McDonalds and why their $3.99 Lobster roll was always so good. The lobster suppliers would always give them first pick because they were afraid of losing such a big contract. One thing I am certain about is that suppliers to Bushmaster do want to give them the best quality work.

  2. #112
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    Quote Originally Posted by militarymoron View Post
    specifically designed go/no-go gauges would also work, depending on the tolerance. it's quicker than a CMM and doesn't require a person trained on the machine.
    Also very low cost, low maintenance, etc. I would be shocked if companies in discussion weren't using them.

  3. #113
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    This excellent discussion on extractor springs has been moved/continued here

    https://www.m4carbine.net/showthread.php?t=435&page=9
    Last edited by Clint; 12-09-11 at 23:04.
    Black River Tactical
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    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
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    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

  4. #114
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    Quote Originally Posted by rsilvers View Post
    I am asking if you think that an original M16 rifle spring, with an o-ring, and an insert - would have too much extraction force on an M4. Or if you just meant that that combination with a spring that was not an original M16 rifle spring would have too much force.
    I don't have any data to support it, but I think you might be right that an original spring/buffer and o-ring would probably be just about right for a carbine length gas system.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  5. #115
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    Quote Originally Posted by rsilvers View Post
    Maybe it does not prove anything useful in the field, but the torque test would prove that it meets the military requirements for coming-undone-ness - and was properly staked.
    I'm trying not to get into a semantics argument on this one, so I'm just gonna leave it alone.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  6. #116
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    Quote Originally Posted by Failure2Stop View Post
    I don't have any data to support it, but I think you might be right that an original spring/buffer and o-ring would probably be just about right for a carbine length gas system.
    I will need to dig a bit but I am all but certain that is true. If you follow the changes made to get the shorter barrels (gas port size, location, buffer weight, spring rate/length) it should all add up.

  7. #117
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    Quote Originally Posted by rsilvers View Post
    That test is next to useless because essentially all bolts pass it, and a tougher test would be too destructive. Many of us have bolts in our ARs right now with thousands of rounds on them that would fail MPI if tested today, yet we still keep them in our rifles. AR bolts crack with use - they just do. We know today, but maybe not 50 years ago, what that means in real-world terms - that the bolt should be replaced at 5000 rounds for super hard use, or 10,000 rounds for typical use, or when it fails if we don't really care.
    I have replaced somewhere around 15 broken bolts and dozens of others, all from guns used at my schoolhouse under my direct supervision. The ones that broke did not have round-counts on them, as my predecessors did not keep gun logs, so I can't comment on how many rounds on average it took to break a bolt, but on the ones we replaced, they were between 10 and 15k, or if they failed headspace but not throat erosion. I had barrels fail throat erosion before 10k.
    I have never double pressure-tested a bolt. Have you?
    I am asking out of curiosity since you brought it up. I don't think I have ever heard of anyone retesting after several thousand rounds.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  8. #118
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    Dimensional inconsistencies will create more stress in an AR bolt which lead to early failure. It's critical that not only the tolerances be held but that they are in control.

    Being in tolerance is important. Dimensions must be within the minimum and the maximum. Just as important is control. If some bolts are at the minimum, some at the maximum and some somewhere in between, the manufacturing process is out of control. Will a simple go-no-go gauge identify an out of control process? Probably not, especially if the inspector is trained simply to look for a go or no-go condition.

    Mr. Silvers, BM has a long way to go before they establish themselves as a top quality manufacturer. As you are a representative of ACC which, as I understand, is part of the Freedom Group, I'm certain you are going to defend BM as a sister company. That's understandable. However, you're playing to a tough crowd. Simply claiming that it's believed a certain manufacture does or does not perform certain tests is not enough, especially if it is not first hand knowledge. Whether Colt does or does not isn't important. What's important is that Colt has a proven track record, therefore what Colt does or does not does work. Bushmaster (and certain other makers) have a tarnished track record. Stick with first hand knowledge of what BM does or does not but more importantly, prove that it works. Bushmaster needs to build and maintain a good track record if they ever hope to gain the reputation as a maker of serious ARs
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
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    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

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  9. #119
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    Quote Originally Posted by Failure2Stop View Post
    I have never double pressure-tested a bolt. Have you?
    We fired 58 300 AAC BLACKOUT proof rounds on one of our bolts. They were about 75,000 psi. That bolt is now in my home defense rifle. I have absolutely no concern about it.

  10. #120
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    Quote Originally Posted by rsilvers View Post
    We fired 58 300 AAC BLACKOUT proof rounds on one of our bolts. They were about 75,000 psi. That bolt is now in my home defense rifle. I have absolutely no concern about it.
    Don't worry, I'm concerned enough for the both of us... That's well beyond the rated life of a bolt.

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