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Thread: Reliability problem with AC556F

  1. #11
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    Quote Originally Posted by Bret View Post
    Are the bolts headspaced to the barrel like an AK or are they interchangeable between barrels like an AR15?
    They are head spaced but Iíve seen people swap them.

  2. #12
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    Quote Originally Posted by Bret View Post
    Are the bolts headspaced to the barrel like an AK or are they interchangeable between barrels like an AR15?
    Officially, bolts are "fitted" and headspaced. Ruger is funny about bolts and bolt components. Practically, you can swap for this diagnosis. Use high-quality domestic .223 ammo.
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  3. #13
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    I have three different 223Rem loads, so that shouldn't be a problem. I also have a headspace comparator, so I can immediately check the spent cases to see if they're within spec. Now that I think about it, I don't recall seeing a serial number on the bolt. If it's critical that the bolt remain with the rifle, you'd think the bolt would be serial numbered. They could be easily mixed up in an armory. Of course I could have missed it.

  4. #14
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    Quote Originally Posted by Bret View Post
    I have three different 223Rem loads, so that shouldn't be a problem. I also have a headspace comparator, so I can immediately check the spent cases to see if they're within spec. Now that I think about it, I don't recall seeing a serial number on the bolt. If it's critical that the bolt remain with the rifle, you'd think the bolt would be serial numbered. They could be easily mixed up in an armory. Of course I could have missed it.
    No serial numbers unless specifically requested on a contract. Ruger's restricts bolts and FPs to factory service only citing required fitting, even for armorers. Last I ordered, extractors were available though.

    FPs got to be a pain, and if sending a gun in I would usually ask for a spare bolt or spare FP to be fit while it was there.
    2012 National Zumba Endurance Champion
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  5. #15
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    I did receive an email reply from Ruger today regarding the screw torque specifications. The gunsmith stated "We set the torque spec here at the factory with air pressure, not a normal torque specification. Screws do not require a great amount of torque. The torque of the screw is not what holds the screw in place but rather staking the threads of the screw is what holds them in place. The low screw tension gives the barrel some room to expand while shooting. This is particularly important in the AC-556." So that's definitely helpful information, but I don't know how anyone can reinstall the screws without knowing the torque specification. I guess the bottom line is that I need to get some more screws and then have someone stake them to "low screw tension".

  6. #16
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    Quote Originally Posted by Bret View Post
    I did receive an email reply from Ruger today regarding the screw torque specifications. The gunsmith stated "We set the torque spec here at the factory with air pressure, not a normal torque specification. Screws do not require a great amount of torque. The torque of the screw is not what holds the screw in place but rather staking the threads of the screw is what holds them in place. The low screw tension gives the barrel some room to expand while shooting. This is particularly important in the AC-556." So that's definitely helpful information, but I don't know how anyone can reinstall the screws without knowing the torque specification. I guess the bottom line is that I need to get some more screws and then have someone stake them to "low screw tension".
    Interestingly, one of the several tweaks for mini accuracy is to torque the screws tighter than spec and evenly.
    2012 National Zumba Endurance Champion
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  7. #17
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    I sent pictures to Ruger and received another reply from the same helpful gunsmith. He said that based on the pictures he would suspect that the extractor is not holding the case tight against the bolt face so he suggests checking the extractor tension. It may be as simple as needing a new extractor spring. Hopefully I'll get a chance this weekend to field strip both rifles and compare the extractor tensions.

  8. #18
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    I decided to swap all of the bolt parts (save for the bolt and firing pin) between both rifles. This rifle is already a PIA because you have to remove the pistol grip to remove the trigger group assembly to remove the stock to remove the recoil spring to remove the op rod to remove the bolt. However, once I got down to disassembling the bolts it went from PIA to near impossible. After stabbing myself in the thumb with a screw driver and about two hours of trying different tricks, I finally got both bolts disassembled.


    I could find absolutely nothing that seemed wrong with the bolt parts from the one that's having the problems. So, I swapped all the bolt parts save for the bolt and firing pin. Fortunately, reassembly of the bolts were easier (not easy) in reverse order.


    Unfortunately, reinstallation of the trigger group assemblies were both a PIA as well. I can't imagine a military force of much size maintaining these rifles. Now that both rifles are back together with their respective bolt bits swapped, I'll take them shooting tomorrow to see if the reliability issues follow the bolt bits or stay with the same rifle.

  9. #19
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    I took both of my AC556F's to the range Sunday. I put 50rds of Fiocchi 55gr FMJ through the older one (that has the bolt pieces from the newer one installed) and it ran 100%. I put 100rds of Fiocchi 55gr FMJ and 60rd of IMI 55gr FMJ through the newer one (that has the bolt pieces from the older one installed) and six failures to eject and or feed. There were also four instances when the action hesitated momentarily. Conclusion: The extractor and ejector are not the problem.

  10. #20
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    Quote Originally Posted by Bret View Post
    I took both of my AC556F's to the range Sunday. I put 50rds of Fiocchi 55gr FMJ through the older one (that has the bolt pieces from the newer one installed) and it ran 100%. I put 100rds of Fiocchi 55gr FMJ and 60rd of IMI 55gr FMJ through the newer one (that has the bolt pieces from the older one installed) and six failures to eject and or feed. There were also four instances when the action hesitated momentarily. Conclusion: The extractor and ejector are not the problem.
    Action hesitated how?
    While shooting?
    While manually cycling?
    Bolt traveling rearward or forward (if you could tell)?

    At least you can eliminate a few parts.

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