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Thread: Short Cycling

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    Gunco Rookie KG1880's Avatar
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    Default Short Cycling

    I have a DPMS that short cycles, and I am out of ideas! I suspected the gas system, so I put in a new 1-piece gas ring and replaced the gas tube. The gas key is secure and staked firmly in place. The only other thing is the spring, but the guy I got the gun from said he replaced the spring before I got it. Any ideas? One last thing, with one round placed in the mag, I can load and fire the round without the bolt holding open...

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    gunco irregular moleman's Avatar
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    Sounds like the guy you got it from ditched his problem onto you. I've seen ar15 run ok with only 2 gas rings, so I don't think its a gas ring problem. Why did the guy replace the recoil spring, and did it run ok before he did that? Have you tried shooting it with a different type of ammo? If you have access to another known good bolt and carrier you could try swapping them out to help eliminate that as a problem. You might also want to check for leaks around the junctions of the front sight base and the barrel and gas tube areas. What is the length of the barrel? Here's a thread where most of the normal suggestions you'll get are covered.http://www.gunco.net/forums/f262/sho...-advice-48568/
    For your bolt catch not working, take off the upper receiver and insert an empty mag. Does the tail on the bolt catch that sticks into the mag well get pushed up by the mag follower? Does the mag catch move freely and not bind? If its just a little gritty try flushing it with cleaner and working it back and forth a bunch of times to work out any gunk. If the previous owner has dry fired the gun without the upper in place it may have bent the mag catch and ruined it.
    Last edited by moleman; 10-12-2009 at 05:29 PM. Reason: spelling

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    Gunco Rookie KG1880's Avatar
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    I read somewhere to use the one shot test to see if the bolt is coming back far enough to re-load the next round. I was just throwing that in there to let you know that I did do that test, and it failed. The BHO works fine otherwise. I noticed soot around the gas tube where it met the front sight block, so I put in a new tube. The new tube fit pretty snug, but the old one did too! The recoil spring was replaced to fix the problem, but never did. The upper is a 20" heavy barreled upper.

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    Gunco Veteran Markp's Avatar
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    Take a close look at the extractor... Acts a lot like short stroking causing all sorts of problems. I put a #60 o-ring under the extractor and like magic, my problems disappeared. You might make sure that air flows freely through the gas tube... I had the front sight a bit off too. Once re-aligned, worked better.

    Mark

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    Gunco Member iansstud's Avatar
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    stock a2 gas block?

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    Gunco Regular chopper's Avatar
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    you could try opening the gas hole in the barrel

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    Red Jacket Firearms's Avatar
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    Quote Originally Posted by chopper View Post
    you could try opening the gas hole in the barrel
    before I did that I'd try putting a bit of a campher on it . Often , will make all the difference and you're not over gassing . To the OP , DPMS is famous for tight .223 chamber's ,ofteen marked 5.56 , somthing to be aware of but I don't think that's your immediate problem . You never said what ammo ?
    Will Hayden, RedJacket Firearms
    www.Redstick-Firearms.com

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    Gunco Rookie KG1880's Avatar
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    I have tried remington, win., and wolf to no avail. I am really suspecting the spring for some reason. Is there a different spring for a carbine vs. rifle? Does anyone know how much tension (in lbs. or oz.)that should be on the charging handle when pulled back 100%? Yes, it is a stock a2 gas block.

  9. #9
    gunco irregular moleman's Avatar
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    Yes there is, the standard fixed rifle type spring should be about 12" long and the car retractable type stock spring should be about 10" long. Red Jackets suggestion about beveling the top of the gas hole is a good suggestion and has worked for me in the past when the gas port in the front sight base didn't line up well with the gas port in the barrel. But thats not where I'd start out either.

  10. #10
    No Hope For Me Coils's Avatar
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    When you replaced the recoil spring, was it the same type?
    I know someone that has a Bush Master 20" with fixed stock and had the same problem, he put in a softer recoil spring and it worked fine.
    "Government is not the solution to our problem, government is the problem" Ronald Reagan

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