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Thread: Fail to pick up a round?

  1. #1
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    Fail to pick up a round?

    Story:
    Buddy and I along with Buddy's wife are out shooting.

    Equipment:
    Buddy's gun is a stock Smith and Wesson M&P15 and brand new P-Mags

    Ammo:
    Wolf Steel Case 55gr FMJ

    Wife, who is small in stature, shoots two shots and the AR seems to short stroke with a fail to pick up a round from the mag. Repeat a few times.

    Buddy shoots the rest of the mag no problems; I also shoot a mag with no problems

    Wife again two shots and then a click as before; but both Buddy and I do not have these problems.

    Does anyone know what could be going on?
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  2. #2
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    She is not holding it tight against her shoulder, creating the semi auto rifle equivalent of limp wristing.

  3. #3
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    Quote Originally Posted by kmrtnsn View Post
    She is not holding it tight against her shoulder, creating the semi auto rifle equivalent of limp wristing.
    +1 Most likely the problem along with the lower pressure wolf. You could try some 5.56 ammo with her holding it like she did before just to test it out.

  4. #4
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    Several things play into this. As Thomas mentioned, the low powered Wolf is a big contributor, that combined with a stiff recoil spring and the rifle moving with the recoil impulse prevent the bolt from traveling far enough to the rear to cycle completely. I didn't know it was possible to "limp wrist" a rifle until I started spending more time behind the firing line as an RSO than on the line and saw it happen.

  5. #5
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    Wolf is weak, add a weak shooter and you get short strokes.

    Cameron

  6. #6
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    Now Cameron has the opportunity to post photos of a female shooter demonstrating proper grip and shooting platform with the AR Series weapons system.

  7. #7
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    We were sort of figuring that. Thanks for the replies
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  8. #8
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    OK, after further testing we have determined that the S&W M&P15 is short stoking, doesn't matter what mag we use. It happens pretty routinely with Wolf ammo but we have also gotten to happen with XM193 5.56NATO ammo; holding the carbine loosely. We have examined the gas system; carrier key, gas rings etc. all seem good to go.

    The carbine is totally stock, purchased in 2008 (in house S&W not a Stag). My buddy and I are rather concerned as this is a go to carbine.

    I do not understand how a S&W, which I am told has large gas ports carbine buffer etc. could short stroke on even Wolf ammo much less XM193 ammo.

    Now with that said is there anyway to test the gas system without any special tools?

    Also, I had a crazy though almost seems opposite in thinking but could replacing the carbine buffer with a heavy buffer or H2 buffer help? Thought being that it would take longer for the buffer spring to over come the heaver inertia? Am I way off base in thinking that the heaver buffer could increase reliability?
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  9. #9
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    Exactly how are you determining the short stroking?
    Bolt consistently not locking back on the last shot?
    Is the bolt closing on an empty chamber?

    Does the recoil impulse feel different and by that I mean does it feel like the buffer is hitting the bottom of the buffer tube when it cycles and or does it feel like it is cycling slow?

    I have had 2 short stroke failures from what I believe was from UMC ammo a while back and on my LMT it felt as if it was cycling slow and I didn't feel the thump of the buffer bottoming out in the buffer tube.

  10. #10
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    most short stroking issues that I've come across were due to leaky gas keys, an easy check if you have access to an air compressor, blow gun with rubber tipped nozzle and some oil.
    apply some oil around the gas key were it meets the carrier, while holding the bolt in the locked postion apply air pressue with the rubber tipped blow gun into the gas key and look for air bubbles around the area were the key makes contact with the carrier. air bubbles equals leaky gas key and will need to be removed and sealed.
    ARIZONA ARMORY PHOENIX, AZ AZARMORY@MSN.COM

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