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Thread: Phosphate under gas block

  1. #91
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    Quote Originally Posted by rsilvers View Post
    I wish there was a way for you to CMM them both, but those machines are $75K.
    I assume you are referring to a Coordinate Measuring Machine?

    I don't doubt that they are dimensionally the same. Heck, they might be sourced from the same manufacturer.

    What counts more so is the processing after the initial machining. Shot peening, heat treatment, and to a lesser extent HPT and MPI.

  2. #92
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    There is this $700 spring design software that I use:

    http://www.smihq.org/public/software/asd6.html

    All of the extra power extractor springs that are popular - I bought them and put them into the software - and it flags them as outside of good engineering practice.

    The original M16 spring, however, was clearly designed by someone who knew what they were doing, as the software says it is great and has stress within normal limits.

    The problem is, carbines need more extractor force than the M16, so the original M16 spring is not quite good enough. There are two ways to solve it - use a stiffer spring (but then they are over-stressed because, given the tiny cavity they sit in, wire of a desirable thickness will no longer fit for these springs with more force) - or use an o-ring with the original spring.

    The o-ring is the correct solution, and not a gimmick - as it is the only solution where you get more extractor force without a spring design that is over 45 percent of the material's tensile strength.

    We went one step further, and made the original spring out of higher grade wire - Rocket Wire, but did it without making it stiffer, so the higher grade material serves simply to make it last even longer.

  3. #93
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    Shot peening is super important, but I don't think any of your favorite companies shot peen their own bolts.
    Last edited by rsilvers; 12-08-11 at 01:11.

  4. #94
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    Quote Originally Posted by rsilvers View Post
    There is this $700 spring design software that I use:

    http://www.smihq.org/public/software/asd6.html

    All of the extra power extractor springs that are popular - I bought them and put them into the software - and it flags them as outside of good engineering practice.

    The original M16 spring, however, was clearly designed by someone who knew what they were doing, as the software says it is great and has stress within normal limits.

    The problem is, carbines need more extractor force than the M16, so the original M16 spring is not quite good enough. There are two ways to solve it - use a stiffer spring (but then they are over-stressed because, given the tiny cavity they sit in, wire of a desirable thickness will no longer fit for these springs with more force) - or use an o-ring with the original spring.

    The o-ring is the correct solution, and not a gimmick - as it is the only solution where you get more extractor force without a spring design that is over 45 percent of the material's tensile strength.

    We went one step further, and made the original spring out of higher grade wire - Rocket Wire, but did it without making it stiffer, so the higher grade material serves simply to make it last even longer.
    Very interesting. What are the repercussions of using a spring that is over-stressed? It just wears out faster? Breaks?

    The O-ring is a modification that I absolutely believe in for carbines. My personal rifle is currently a 20" with rifle gas system (by choice, I specifically sought that configuration) so it is not of major concern to me... I use the 3-coil spring and a black insert. (And I don't think this is a genuine black insert... feels too soft.)

    This is really neat information, I'm glad you're so open about sharing it.

  5. #95
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    I am a licensed aviation technician and deal with the issues of torquing and locking fasteners every day

    Quote Originally Posted by rsilvers View Post
    Just try to unscrew the screws with 55 inch-lbs of torque. If the screws don't move, the staking is good.
    ETA: My apologies to all on this forum. I posted the following which is incorrect-

    The proper way to verify torque is to set the torque wrench to the correct torque and tighten.

    Total torque of the gas key bolts is 55 in/lbs + torque from staking. Specification for torque + staking is 55 in/lbs - 100 in/lbs. Verification would require setting the torque wrench to the nominal torque, which is halfway between minimum and maximum. That would be 77.5 in/lbs. Rounding up to 80 is acceptable. Apply 80 in/lbs of torque after staking to verify final torque.


    After posting, I realized that re-torquing a staked bolt is poor procedure. One, there is a risk of compromising the mechanical lock feature of the stake. Two, if the staking is on the minimum side, it would be possible to over-torque the bolt. The proper way to check the torque of a staked bolt would be to break torque, then torque using the proper procedures. It's been a long week with too little sleep

    The following about torque wrenches is correct- It takes a special torque wrench to be certified accurate in a counter-clockwise direction. Most torque wrenches are designed to give an accurate reading in the clockwise direction only. Even if you were to verify torque by attempting to loosen, you should still tighten afterwards or better still, break torque completely and re-torque and re-stake.

    Quote Originally Posted by lamarbrog View Post
    ... I hate to argue with someone with credentials such as yourself on technical matters... but staking is there in the event that over time the screws wiggle loose. Staking is not to tighten the screws.
    Quote Originally Posted by lamarbrog View Post
    ...The staking is there to save your butt if the get loose from some reason over time, or were not torqued properly to begin with.
    Staking is a mechanical lock to prevent the bolts from coming loose, not to catch them after coming loose. Properly staked bolts will stay torqued by increasing the amount of torque needed to remove (or tighten) the bolt

    Properly torqued gas key fasteners, in a perfect world, would not need staking at all. Staking is a backup.
    If this were true, Young carriers would be a good choice as they take steps to ensure the surfaces of the carrier mate to the surfaces of the gas key and use a sealant between them and torque to 55 in/lbs.

    The staking is part of the torquing process. It gives a higher torque without stretching the bolt and threads to the point of failure and has the additional advantage of being a mechanical lock
    Last edited by MistWolf; 12-08-11 at 18:19.
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  6. #96
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    Quote Originally Posted by rsilvers View Post
    The reason Colt got an unfair deal in the 'dust' tests was that the govt picked M4s off the shelf that had cyclic rates at or below 700 rpm, and competed them against XM8s and SCARs which were specially prepared by Hk and FN for this event - no doubt with cyclic rates optimal for dust tests (higher rates).
    Source for this?

    Quote Originally Posted by rsilvers View Post
    Would you really ream a chrome lined barrel?
    Absolutely.
    You wouldn't?

    Would you really toss a Bushmaster bolt without checkin it? How do you know it is not mil spec now?
    Because there is absolutely no indication that it is to spec since they aren't individually tested.

    Why would you stake the carrier key when it is already staked?
    When the staking is insufficient to do the job.

    Quote Originally Posted by rsilvers View Post
    Just try to unscrew the screws with 55 inch-lbs of torque. If the screws don't move, the staking is good.
    What torque tools are you using to perform this task?

    Quote Originally Posted by rsilvers View Post
    It is very unlikely that a BCM bolt is better than a Bushmaster bolt.
    Support data?

    Quote Originally Posted by rsilvers View Post
    Which spring is good?
    Is this a question to legitimately seek information or to expose a lack of knowledge/information?

    Quote Originally Posted by rsilvers View Post
    The o-ring is the correct solution, and not a gimmick - as it is the only solution where you get more extractor force without a spring design that is over 45 percent of the material's tensile strength.
    Yet the o-ring has been repeatedly found to result in excessive extractor tension in real use.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  7. #97
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    Quote Originally Posted by Failure2Stop View Post
    Yet the o-ring has been repeatedly found to result in excessive extractor tension in real use.
    With an original M16 rifle extractor spring?

  8. #98
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    Quote Originally Posted by rsilvers View Post
    With an original M16 rifle extractor spring?
    I can't figure out why anyone would put an o ring on a rifle extractor spring in stead of just replacing the rifle spring with the 5 coil spring and Black/Green insert.
    "You people have too much time on your hands." - scottryan

  9. #99
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    Quote Originally Posted by Failure2Stop View Post
    Because there is absolutely no indication that it is to spec since they aren't individually tested.
    What do you mean by individually tested? Which maker verifies that each bolt meets all specs?

    Quote Originally Posted by markm View Post
    I can't figure out why anyone would put an o ring on a rifle extractor spring in stead of just replacing the rifle spring with the 5 coil spring and Black/Green insert.
    The rifle spring is the only one which has stress of less than a 45% of MTS.

    Springs must not be referred to by the number of coils because they are reference values and change from batch to batch, even for the same design.

    Quote Originally Posted by Failure2Stop View Post
    Source for this?
    http://www.usni.org/magazines/procee...happened-wanat

    According to officials at Colt, those reasons included the fact that six of the ten M4s drawn for the test did not meet the minimum rate of fire of 700 rounds-per-minute mandated under Mil-Spec IAW Mil-C-70599A(AR), which requires a cyclic rate of fire of 700 to 970 rounds-per-minute. The M4s used in Dust Test 3, delivered to the Army in June 2007, met mil-specs when delivered; however, together the ten drawn for the test from the U.S. Army inventory averaged only 694 rounds-per-minute.30 While performing comparably with the HK416, XM8, and Mk16 in all other respects, the M4 carbines used in the test experienced a large number of failure-to-feed and failure-to-extract stoppages.31 Colt says this is because of the sub-mil-spec rate-of-fire of the test weapons.

    Colt also states that ATEC's testers were unfamiliar with the M4s' 3-round burst configuration which, depending on the position of the cam, will sometimes fire 1 round or a 2-round burst before firing a 3-round burst. This unfamiliarity, said Colt, led to single rounds and 2-round bursts being counted as stoppages. With the exception of the M4s, all other weapons tested were fully automatic with no 3-round burst provision. Further, Colt points out that the test itself did not meet Mil-Spec 810F and "was not repeatable."

    In response to what Colt described as "the premature media reporting" of the raw test data, Program Executive Office Soldier suggested that Colt conduct its own extreme dust test. So Colt contracted a DOD-certified testing agency, Stork East-West Technology Corporation in Jupiter, Florida, to conduct its own dust test according to mil-spec guidelines. In this test of ten M4 carbines, which was conducted under a protocol identical to that used in Extreme Dust Test 3, only 111 stoppages were reported.
    Quote Originally Posted by Failure2Stop View Post
    When the staking is insufficient to do the job.
    Of course, but it is unlikely to be insufficient.

    I guess we can go back for years and find bad examples - but no one has yet shown they can go buy a new Bushmaster and that the staking would fail the test that MistWolf described - applying 80 inch-lbs of tightening torque and seeing the bolt move.

  10. #100
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    Quote Originally Posted by rsilvers View Post
    What do you mean by individually tested? Which maker verifies that each bolt meets all specs?
    I hate to answer a question with a question, but are you saying that Colt does not?

    I was more referring to the assertion that HK and FN intentionally modified their submissions.

    Quote Originally Posted by rsilvers View Post
    Of course, but it is unlikely to be insufficient.

    I guess we can go back for years and find bad examples - but no one has yet shown they can go buy a new Bushmaster and that the staking would fail the test that MistWolf described - applying 80 inch-lbs of tightening torque and seeing the bolt move.
    This test could easily be passed without ever staking the key, so I am not all that convinced that the test proposed proves anything useful. Frankly, I would rather just have the gas key be an integral part of the BCG, as I have no need to ever swap them and it would remove a potential failure point. However, that is neither here or there. What I have seen is those with visually weak staking (such as BM) have gas keys shoot loose. Haven't seen it ever in extremely high round count Colt M4s or M4A1s, which to me seems to imply that someone is doing it right and someone else isn't.

    Quote Originally Posted by rsilvers View Post
    With an original M16 rifle extractor spring?
    Just spring or spring and buffer?
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

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