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Thread: Diagnosis check...bolt speed?

  1. #31
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    Quote Originally Posted by uncle money bags View Post
    I thought the bcg at rest was already in its lowest position, and that as it travels to the rear and the skid clears the round stack the next round will actually move up a fraction of an inch, well in advance of the bcg as it returns to battery.
    Are you claiming the bcg pushes the rounds down when it travels to the rear?
    We are on the same page, the downward pressure (from the BCG) is already there, essentially the magazine spring is the only thing resisting this. But since there is a "stack" of ammunition above it there is a "moment of inertia" (column inertia) that takes a bit of time to "get moving". Hence why I said that a "just under full" magazine should be the most prone to this. Essentially the same effect as a mag spring that has lost some tension and is beyond service limits. It cant push the "column" of rounds up fast enough. I believe that a BCG velocity that is extremely high could duplicate the same effect. After all Mr. Stoner had to have had a "spec" for minimum magazine spring tension. He would have based this on a 20" barrel and rifle buffer. Compare the BCG velocity of:

    16" (carbine gassed) barreled Semi auto carrier with a carbine buffer.

    20" (Rifle gassed) barreled M-16 carrier with rifle buffer system.

    I dont know the "numbers" but it wouldn't be hard to figure the carbine velocity much higher...

    In the simplest terms, if anyone can believe an old worn out mag spring can cause the same malfunction, then you must also believe an "in spec" mag spring can fail to be sufficient if the spec it is "up to spec" for was written for a very different configuration (20/rifle/auto carrier, etc. vise 16"/carbine/semi-auto carrier)

    Quote Originally Posted by steyrman13 View Post
    Is it a Stag left-handed model? 1500 would be over your left shoulder around the 7-8 o'clock position....or the brass circled 360 deg around you back to the 3 o'clock position! That's wild!!
    Maybe the latter and that's why it was only two feet away, but that would mean really strong ejection to create a whirlwind!
    You bump your head? 15:00 is "3 o'clock" which would be straight out the ejection port in a straight line to the right of a right handed shooter.

    Or are you messing with me and im too tired to comprehendo?

  2. #32
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    Quote Originally Posted by Mall_Ninja View Post

    You bump your head? 15:00 is "3 o'clock" which would be straight out the ejection port in a straight line to the right of a right handed shooter.

    Or are you messing with me and im too tired to comprehendo?
    Messing with you. You used 24 hour time. If you look at a 24 hour clock(mil clock) there is two versions. 24 hour marks where 1500 sits at around the 7-8 o'clock position of a normal clock, or where the hour hand travels a full circle and then lands back at the 3 o'clock position on second time around. I was just joking saying no reason to say 1500 instead of 3.....


    Even though the spring was the correct length, is it possible it is a cheap brand that isn't the correct spec...metal composition and spring rate too weak?
    If it is a PSA hammer forged upper, I would think the upper is fine but not guaranteed. Hopefully you can test it on your DD lower if they come back.
    I just noticed it was PMC bronze. Isn't that known to be weak ammo? Try some quality ammo or even xm193 or something to see if it still happens. That would alleviate if it is short stroking or bolt out running. Also try the last round lock test.
    Last edited by steyrman13; 08-20-13 at 01:22.

  3. #33
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    Quote Originally Posted by steyrman13 View Post
    Messing with you. You used 24 hour time. If you look at a 24 hour clock(mil clock) there is two versions. 24 hour marks where 1500 sits at around the 7-8 o'clock position of a normal clock, or where the hour hand travels a full circle and then lands back at the 3 o'clock position on second time around. I was just joking saying no reason to say 1500 instead of 3.....
    HA! Thats funny, actually at the time it was faster to type 1500 rather than 3 o'clock, to which I ended up going back and putting 15:00 so it wouldn't get confused, then realizing how going back to add the "colon" wasted more time than typing 3 o'clock to begin with! Derrr...

  4. #34
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    Quote Originally Posted by Mall_Ninja View Post
    If the BCG velocity is high enough, I believe the sudden downward pressure as the BCG moves rearward can push the ammo stack down into the mag enough to cause an air gap.
    How exactly is this sudden downward pressure generated?

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