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Thread: 11.5" BCM Short stroking

  1. #21
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    Quote Originally Posted by matemike View Post
    By hand the bolt locks back every time, even when trying to do it as fast as possible. So I know the follower and bolt catch are good.

    With the V-max, it locked back 50% of the time. 40% it did not lock back, 10% of the time the last round jammed between the bolt face and feed ramps so I did not get a chance to fire the last round.
    I would probably DX that round even if you resolve the issue by some other means. I wouldn’t use it for hog hunting either. There are some better hog hunting choices out there. To be honest I don’t use any type of plastic/polymer tipped rounds in my AR’s. If I use them and I have in the past, I use them in bolt guns. I don’t think I have the case for the ammo I use for hog hunting but I want to say it’s a 60gr Your 11.5 should handle it well. My 10.3 does. I’ll try to find the name of the ammo and post it.


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  2. #22
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    Everything OP has posted throughout this thread leads me to believe that:

    1) The gun is very over-gassed.
    -or-
    2) The pressure curve for THIS SPECIFIC ROUND simply hits very hard at that gas-system length.

  3. #23
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    1 O’clock and solid ejection.
    What are indicators that the bolt is going too fast? I mentioned that some rounds were being picked up by the bolt dragging across the top of them and wedging them between the bolt face and feed ramps. Some rounds were pinched so bad that they looked like there were sliced open down the case wall. Bolt too fast?[/QUOTE]

    1 o'clock sounds like it's over gassed. When my 11.5 bcm did that I put in an h2 buffer and the problem was solved with the ejection pattern returning to the 3 o'clock. . I'm thinking this is causing your lock back issue as well, imo your bcg speed is out running the mag springs ability to lift the mag catch before the bcg can catch it.

  4. #24
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    This is why the ejection pattern should not be used to troubleshoot an AR. The carrier not locking back is caused by short stroking. Short stroking is caused by under gassing. It does not matter what the ejection pattern says, the V- Max ammo is causing short stroking in this AR. Period.

    I think WS6 is right about the pressure curve of the ammo being the root cause of the malfunction.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

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  5. #25
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    I find it very hard to believe that with the setup that he is using that any comercial round would cause short stroking especially with an aac can on it. The simplest thing to do OP would be to take your can off and if the problem persists then that would lead toward further investigation. If not the increased cyclic rate is most likely your problem

  6. #26
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    Made a few strings of fire this weekend.
    The V-max's, M855 and some remington 55gr jacketed hollowpoints as well as remington 55gr PSP soft points. All without can at first. Everything ran perfectly. Bolt always held open too.
    Just to keep things from going "haywire" again on me (malfunctions with v-max suppressed) while I was at my friends hunting ranch I just ran the M855 and 55gr softpoints with the can and all went well. I refrained from trying the v-max's suppressed so I wouldn't get frustrated while I was supposed to be enjoying myself.

    I shot a hog with the 55gr 223 soft point and it performed.

    I gotta go back and run these v-max's suppressed at the shooting range and see what sort of results I get. So far that's the only way I've ever had a problem with this gun. I might have stumbled onto the one round it doesn't like when suppressed...? I have a ST-T2 in another gun and a carbine buffer in my spares to try at the range. See what side of the spectrum I'd need to go from a H buffer to get it to run better.
    Last edited by matemike; 10-13-19 at 21:53.
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  7. #27
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    3991FCF0-46E4-41F4-A489-438385EED620.jpg

    50 yards, Aimpoint T1, free handed, right between the eyes.
    “Twenty years from now you will be more disappointed by the things you didn’t do than by the ones you did do. So throw off the bowlines, sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.”
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  8. #28
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    Nice shot!
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  9. #29
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    Great job!

  10. #30
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    Quote Originally Posted by MistWolf View Post
    This is why the ejection pattern should not be used to troubleshoot an AR. The carrier not locking back is caused by short stroking. Short stroking is caused by under gassing. It does not matter what the ejection pattern says, the V- Max ammo is causing short stroking in this AR. Period.

    I think WS6 is right about the pressure curve of the ammo being the root cause of the malfunction.
    Not locking back can also be caused by extremely violent or rapid cycling.

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