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Thread: Sharps' new bolt head design for M4 PIP bid

  1. #11
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    From a purely observational standpoint, I don't see a drastic increase in bolt failures as a result of the ramped lugs.

    The barrel extension lugs seem to hold up well with about that much 'squared' section and ramps behind them at the throat of the extension.

    I know there are most likely some metalurgical differences between barrel extension and bolt, but beyond that, the revised shape shouldn't be too much of a factor as barrel extensions seem to outlast bolts by a pretty fair margin AFA outright breakage.

  2. #12
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    Quote Originally Posted by bo-hoss View Post
    I use this example for comparason/illustration:

    If you removed 30% of the material from your car or pick up truck frame, would you drive it??
    Or, If you removed 30% of the load bearing material from a bridge you cross daily, would you continue to drive across it?
    Actually, yes on both counts, as long as I was the one determining where and how the material was being removed.

  3. #13
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    Quote Originally Posted by GTifosi View Post
    Actually, yes on both counts, as long as I was the one determining where and how the material was being removed.
    Fair enough..

  4. #14
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    I have no idea how the 3 or 4 post above got out of chronological order.

  5. #15
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    Quote Originally Posted by GTifosi View Post
    From a purely observational standpoint, I don't see a drastic increase in bolt failures as a result of the ramped lugs.

    The barrel extension lugs seem to hold up well with about that much 'squared' section and ramps behind them at the throat of the extension.

    I know there are most likely some metalurgical differences between barrel extension and bolt, but beyond that, the revised shape shouldn't be too much of a factor as barrel extensions seem to outlast bolts by a pretty fair margin AFA outright breakage.

    Comparing the bolt lugs to the extension lugs is apples to oranges.

    The barrel extension lugs are wider (more overall mass/strength) than the bolt lugs.

    Barrel extensions are not made from the same material as mil-spec bolts.

    I'm not sure if the ramped lugs is a issue or not. I use this example for comparason/illustration:

    If you removed 30% of the material from your car or pick up truck frame, would you drive it??
    Or, If you removed 30% of the load bearing material from a bridge you cross daily, would you continue to drive across it?

  6. #16
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    Quote Originally Posted by bo-hoss View Post
    I have no idea how the 3 or 4 post above got out of chronological order.
    It's been happening all over the forum for a day or two now.

    **
    Lemme expand just a bit on the angled lug vs rectangular with an anology of my own:
    You build 2 shelves completely out of 1x6 pine
    The supports are cut to 6" along the side that is going against the wall while the 6" of the width of the board is used to hold the shelf portion and that shelf upon it is 6" deep.
    Both shelves are the same length, anchored to the same wall in the same fashion on studs and have the same number of supports.


    One shelf will hold no more weight than the other if the support is cut with its corners all at 90 degrees into a square shape than it will if cut as a right triangle as the very great majority of the load is being carried in shear by the side along the wall.

    The triangle is a 50% reduction in size along one axis, yet the load support is the same.

    In the instance of the revised bolt, the 'shelf' is on the rear side of the lugs where they abut the barrel extension lugs after lock, the portion in shear is where the lugs meet the bolt body proper.

    **
    Honestly I believe one of the reasons the lugs still retain the rectangular shape is ease of manufacturing, not extra stength.
    Slots can be broached easily enough, which is currently how the lugs are machined for the long axis, but there are extra steps that would be needed to broach then taper, which would likely be done before broaching but still represent 'extra' processes, then radius the top outermost side of the ramp on each of the lugs.

    The KAC version with the radiused lug and bolt areas would actually be easier to produce than the one this thread is about if for no other reason there are really little to no more machining processes involved with broaching the KAC shape vs standard square cut lugs. It's simply a different shaped cutter.
    Last edited by GTifosi; 08-06-11 at 15:16.

  7. #17
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    Has anyone actually had hands on with this. Is supposed improvement reality or hype.

    I'll wait for further info.

    On the roller cam, does anyone think this is an improvement, detriment, or cash cow? No experience with it, just want to know.

  8. #18
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    Quote Originally Posted by bo-hoss View Post
    Comparing the bolt lugs to the extension lugs is apples to oranges.

    The barrel extension lugs are wider (more overall mass/strength) than the bolt lugs.

    Barrel extensions are not made from the same material as mil-spec bolts.

    I'm not sure if the ramped lugs is a issue or not. I use this example for comparason/illustration:

    If you removed 30% of the material from your car or pick up truck frame, would you drive it??
    Or, If you removed 30% of the load bearing material from a bridge you cross daily, would you continue to drive across it?
    I would not, but I would trust that an engineer doing a proper structural analysis can determine what areas can have material removed without adversely affecting the structural performance, or can be done by making a proper material selection.

    Without seeing the stress loading calculations on the front of the bolt lugs to back up the assertion the front of the lugs is actually aiding in resisting the shear loads, that material up front may very well be "dead weight"

    We also don't know what grade of steel or heat treat is being used, which can very much play into the ultimate load resistance capability of the material and design.

  9. #19
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    From the picture, it appears the shape of the bolt lugs can come from a regular bolt profile, minus some material. I fail to see how removing material can make it stronger or better in any way.

    Other designs, like KAC or LMT enhanced have additional material at the base of the lugs in the form of a radius. This shape makes them stronger.

  10. #20
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    Quote Originally Posted by P2000 View Post
    I fail to see how removing material can make it stronger or better in any way.
    'Stronger'?
    Unlikely unless there is a materials change.
    'Not weaker' would be about the limit using the default standard material.

    'Better'?
    Gray area.
    On very low scale levels, the rounded noses and taper of the lugs could allow for easier barrel extension engagement and the lighter weight could allow for faster lock/unlock times and higher BCG cycle speeds.
    Again, very incrementally small %-ages of change, but certainly plausible.
    Whether that is actually better or worse :shrug:


    Other designs, like KAC or LMT enhanced have additional material at the base of the lugs in the form of a radius. This shape makes them stronger.
    I totally agree that a radiused transition is far superior to a sharp angled transition. Sharp corners are where failures generally begin.

    Adding material or not to accomplish it is questionable though.
    Certainly if the radius is quite large there would have to be significant material increase and the weight associated with it, but is that large a radius actually neccisary compared to smaller radii?
    ie: does it need to really be that large with all that extra material, or would it be as mechancially sound if the curves were smaller?

    Dunno.
    But I do know that adding material isn't always the answer to make something stronger.
    Sometimes a subtle shape change with no change in mass, or different engineering techniques and/or materials allow for significantly lighter end results that actually have superior strength over thier 'mass is master' counterparts.

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