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Possible Shortstroking issue.

Discussion in 'Black Rifle Forum' started by Foxtrotx1, Dec 4, 2011.

  1. Foxtrotx1

    Foxtrotx1

    4,036
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    Jan 29, 2010
    Scottsdale AZ
    For the last year I have owned a DPMS Chromlined 16inch Carbine upper mounted to a firebird lower. Parts kit is DPMS.

    About 8,000 rounds through the rifle. Not a single issue until I hit about 7,400 rounds. Suddenly, after thousands of rounds of steel case, it has begun short stroking with both TULA, and WP (happens less with wolf). Removed ST2 buffer in lieu of a carbine buffer and now it happens less, but still occurs.

    Problems do not occur with high pressure NATO ammo. Leads me to believe I may have an issue with the gas rings or the gas tube. The mushroom on the gas tube appears to be gone.

    Carrier is well staked. Is not a full auto carrier.
    Bolt does not fall out under gravity.

    Parts added when I first got the rifle: Gunfighter MOD3 charging handle, ST2 Buffer, EOTECH XPS2, Daniel Defence EZ CAR, Houge grip, Vortex FlashHider.

    Using a variety of mags, happens with all of them. PMAGS, USGI with magpul follower and LANCERs.

    I keep the rifle very clean and well lubed with MOBILE 1.

    Any Advice (besides dumping it and buying a COLT/LMT/DD/BCM.)?

    :wavey:
     
  2. bmoore

    bmoore

    4,376
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    Jan 15, 2006
    Under a regime.
    Im sure you know this, but Wolf and Tula are horribly underpowered. I believe they chrono at around 2700fps (I think more like 2500fps from a 16" barrel) or less. Its weird that your just now having problems. Seems like you keep it clean and wet. Maybe just run what the gun likes, Ive never had a problem with my 20" A2 DPMS upper with any sort of factory rounds, PMC, Federal, Remington it even eats my reloads just fine.

    I ran 60 rounds of Tula through my AR's when a friend gave me 3 box's and you can tell they are weak. My Smith M&P15 and Palmetto dissy ate them fine but my 20" DPMS short stroked with them, and like I said it eats all factory brass stuff and my reloads without issue.

    Have you changed/upgraded your buffer spring?
     
    Last edited: Dec 4, 2011

  3. Foxtrotx1

    Foxtrotx1

    4,036
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    Jan 29, 2010
    Scottsdale AZ
    Have not touched the buffer spring, Something to consider?
     
  4. bmoore

    bmoore

    4,376
    7
    Jan 15, 2006
    Under a regime.
    For $4.50 I would give it a shot. I just ordered 3 new ones from Bravo company for my guns. Every 2-3000 rounds I believe is when they should get yanked. You can also measure it and see if it is ready to be replaced, I do not remember the correct length but I think google will help you there. There will be people that come along after me and post more useful info. My advice is good ammo, good mags, clean and lubed and make sure parts are not worn out.
     
    Last edited: Dec 4, 2011
  5. Glockdude1

    Glockdude1 Federal Member CLM

    24,620
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    May 24, 2000
    Beaumont,Texas
    Change ammo.

    See if anything changes.

    :cool:
     
  6. K. Foster

    K. Foster

    2,600
    509
    Feb 19, 2002
    Mo.
    I concur on changing the buffer spring. My manual shows appropriate length between 10 1/16" and 11 1/4" for carbines but it’s a little dated. Army & Air Force, May 1991.
     
  7. Foxtrotx1

    Foxtrotx1

    4,036
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    Jan 29, 2010
    Scottsdale AZ
    Ill order some BCM buffer springs. I wonder if it's possible that recent tula and wolf ammo is underpowered compared to earlier lots. Also, the temp has dropped 40 degrees in phoenix.....
     
  8. bmoore

    bmoore

    4,376
    7
    Jan 15, 2006
    Under a regime.
    I was going to mention that the new stuff may be weaker. If you can afford to do so, I would stay away from it. That garb prints like 5 inch groups at 100 yards.
     
  9. faawrenchbndr

    faawrenchbndr DirtyThirty fan CLM

    36,273
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    Nov 24, 2005
    Troy
    Change your ammunition,.......
     
  10. WoodenPlank

    WoodenPlank Who?

    7,958
    3
    May 15, 2010
    NW Florida
    This is why I avoid Tula, Wolf, etc for ammo.
     
  11. mvician

    mvician Lifetime Member

    3,149
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    Jun 8, 2007
    NW Indiana
    While you are at it, replace your gas rings and other "wear" items....after 8000 rounds your rifle deserves it. :supergrin:
     
  12. Foxtrotx1

    Foxtrotx1

    4,036
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    Jan 29, 2010
    Scottsdale AZ
    Which Items would you recommend I change?

    Was thinking about doing the gas tube myself, how difficult are the rings?

    When that bolt breaks....i'm def getting a DD or BCM bolt.
     
  13. WoodenPlank

    WoodenPlank Who?

    7,958
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    May 15, 2010
    NW Florida
    Rings are not hard, I've seen a set changed out in a couple minutes. I believe they slip off with just a little wiggling or prying. I get the feeling yours are worn or possibly even have one missing. I had the same issue after about 5k rounds through one bolt, and replacing the gas rings cleared it up. I doubt the gas tube is the issue, but anything is possible.
     
  14. bmoore

    bmoore

    4,376
    7
    Jan 15, 2006
    Under a regime.
    With 8,000 rounds down range I would say you did great. For 130 bucks you can have a LMT or BCM entire bolt carrier group and be off to the races. You can have a Palmetto state armory carrier group for 99 bucks through this month. Roll that DPMS carrier group to spare parts, it did well for you. Put a new one in and it will go another 8,000 without a problem.
     
    Last edited: Dec 4, 2011
  15. surf

    surf

    1,019
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    Jul 7, 2010
    If your shooting the same or similar ammo and you start to have problems that is a good sign that you are more than likely having gas related issues, provided you didn't just get an even worse batch of underpowered crappy ammo. If you are having gas related issues, even good ammo will start to show problems as the situation gets worse.

    If you say that the bell on the end of the gas tube looks very worn that is a good start. Pictures would help. With a poorly aligned gas tube, over time wear on the bell end from excessive rubbing on the gas key can cause enough of a gas leak to show problems. I would also do a quick compression check on the bolt and carrier, but would probably replace the gas rings as that is a cheap and simple thing to do. Remove the bolt carrier group, extend the bolt all the way out and balance the bolt carrier group by setting the face of the bolt on a flat surface. If the carrier collapses under its own weight that is a good sign to change gas rings. Also check the gas key itself and make sure that it isn't coming loose. As has been mentioned check the length of the recoil spring.
     
    Last edited: Dec 4, 2011
  16. Foxtrotx1

    Foxtrotx1

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    Jan 29, 2010
    Scottsdale AZ
    Ill try and get some photos and measurements tomorrow.

    You guys are a big help :wavey: