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Thread: Phosphate under gas block

  1. #71
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    Quote Originally Posted by lamarbrog View Post
    If for some reason all I could get was a Bushmaster.... I'd swap the bolt assembly to a Mil-Spec one, drop a 5.56NATO chamber reamer in it, stake the gas key
    I am not really up on what Bushmaster does. Do we know they are 223 chambers? It would seem more likely they are 5.56mm.

    Would you really ream a chrome lined barrel?

    Would you really toss a Bushmaster bolt without checkin it? How do you know it is not mil spec now?

    Why would you stake the carrier key when it is already staked?

  2. #72
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    Quote Originally Posted by rsilvers View Post
    I am not really up on what Bushmaster does. Do we know they are 223 chambers? It would seem more likely they are 5.56mm.

    Would you really ream a chrome lined barrel?

    Would you really toss a Bushmaster bolt without checkin it? How do you know it is not mil spec now?

    Why would you stake the carrier key when it is already staked?
    If it is 5.56NATO already, it will be unaltered. If it is not already 5.56NATO, then I have no qualms with reaming a chromed chamber. It is hard chrome so there is no flaking risk, and the throat is the main difference which is quickly eroded anyway. Trust but verify-

    Bushmaster, last I looked, doesn't even claim 158 Carpenter steel. They definitely never mentioned any HPT or MPI that I saw. (Not that I place great emphasis on those tests... but generally the companies that perform them are offering a quality bolt.)

    Depending on the quality of the staking, I may stake it better. Or, I may add redundant staking on the top in the "field expedient" or "counter-staking" fashion.

    Obviously, if something is already done and done correctly I'm not going to change it....

  3. #73
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    Bushmaster absolutely uses C158 steel - whether they advertise it or not is another matter.

    As for HPT - yes, they certainly do that.

    As for MPI - I don't actually know. The Brownell's catalog says they do, but it would not be the first time a description was incorrect.

  4. #74
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    Quote Originally Posted by lamarbrog View Post
    Depending on the quality of the staking, I may stake it better. Or, I may add redundant staking on the top in the "field expedient" or "counter-staking" fashion.
    Just try to unscrew the screws with 55 inch-lbs of torque. If the screws don't move, the staking is good.

  5. #75
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    Quote Originally Posted by rsilvers View Post
    Bushmaster absolutely uses C158 steel - whether they advertise it or not is another matter.

    As for HPT - yes, they certainly do that.

    As for MPI - I don't actually know. The Brownell's catalog says they do, but it would not be the first time a description was incorrect.
    Even if it does pass those, if it is heat-treated too deep it will be brittle... the cracks may not appear initially to be seen on a MPI. Give it a couple hundred rounds and *snap*, there went your bolt.

    A new bolt is $65, and it is arguably the most sensitive part of the rifle as far as how well it needs to be made and how easy it can be to screw it up- and it is absolutely 100% critical to function. Personally, I'll pay my $65 to get a BCM bolt (along with the good extractor spring and insert) and not worry about it. Keep the original as a spare.

  6. #76
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    It is very unlikely that a BCM bolt is better than a Bushmaster bolt.

  7. #77
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    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.
    ... 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.

  8. #78
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    Quote Originally Posted by lamarbrog View Post
    (along with the good extractor spring and insert)
    Which spring is good?

  9. #79
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    Quote Originally Posted by rsilvers View Post
    It is very unlikely that a BCM bolt is better than a Bushmaster bolt.
    Okay... I still don't trust Bushmaster for such a critical part. If you wouldn't change it... don't. Personally, I would.

  10. #80
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    Quote Originally Posted by rsilvers View Post
    Which spring is good?
    Gold/Five Coil.

    Black insert, and possibly a Crane O-ring.

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