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Thread: Disengrating AR Buffers and Short Stroking 18 Inchers

  1. #11
    Site Supporter
    Join Date
    Sep 2011
    CT (behind Enemy lines)
    The 18" rifle is likely over gassed and under buffered for its carbine buffer and tube. If you are running hot ammo your BCG could be moving too fast for the magazine to present a new round in time. I would seriously consider a A5 buffer system and probably the H3 buffer to start.

    Also make sure the current buffer spring does not go to solid height before the buffer bumper protrudes.

  2. #12
    Member Kommander`'s Avatar
    Join Date
    Dec 2012
    Thank you for all the helpful replies. I ordered a H-1 buffer, new spring, tungsten weight, and replacement buffer bumper from KAK. This will allow me to test H-1 and H-2 buffer weights in my pistol, repair the carbine buffer to have it as a backup, and have the old recoil spring as a backup as I currently have none.

    As for the rifle it is using a carbine tube/buffer assembly. The ammo is 55 grain Ammo Inc stuff I got when I used to work there. We tried two different mags, a 30 round OKAY and a 20 round Magpul mag. They are both new enough, both age and round count wise, that they should not be the source of the issue. Additionally the two mags work fine in my two ARs.

    I have not yet had an opportunity to look over the rifle but as it stand as soon as we are able we are going to return to the range with my Father's rifle and my two ARs and swap parts around untill we can isolate the issue. The A-5 stock is an interesting idea and if we are unable to resolve the issue I will look into it more deeply


  3. #13
    Just at an overview level, if a rifle is not cycling something is probably wrong with the plumbing. 50,000 PSI is pushing the thing open, if it is not getting pushed open some of that pressure is probably leaking (carrier key) or is blocked (gas block alignment). Even if uppers were factory assembled, some of the gas blocks are just eyeballed into place, probably by somebody that might not be all that familiar with the task.

    Gas block misalignment was the issue in this thread.

  4. #14
    To determine if the AR is short stroking, a lock back check needs to be done. Until a lock back check is performed, we won't know where to begin looking for the problem.

    Insert an empty magazine in the mag well and pull on it to see if it's locked in place. Once the mag is locked in place, pul the charging handle to the rear and check to see if the BCG locks back.

    If it locks back, remove the mag and load it with a single round of full power 5.56. Insert mag and load the round into the chamber. Fire the AR. If the BCG locks back, you don't have short stroking. If it doesn't lock back, the AR is short stroking. If it does lock back, perform the check a few more times until you're satisfied with the results.

    I strongly suggest replacing the extractor spring with a Colt M4 extractor spring. A weak extractor spring can cause all kinds of malfunctions, including a round pushed partially out of the mag that's over ridden by the bolt. Replacing the spring eliminates a possible variable and reduces the chances of just chasing your tail. I know from experience.

    The only makers I'm aware of using the right extractor springs in their builds is Colt, Sionics and SOLGW. Colt of course uses Colt extractor springs. Sionics and SOLGW use Sprinco extractor springs on advice by the late Will Larson who was a very experienced armorer. Most of the other makers use what I suspect is the old M16 extractor spring which is marginal in the shorter ARs.
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  5. #15
    Member Kommander`'s Avatar
    Join Date
    Dec 2012
    My Dad and I finally managed to get out again and test the rifle after I recovered from a bout of Covid. Turns out it was the FACTORY ammo from my former employer, Ammo Inc., that was as causing the issue. With my reloads, which are which are of very average power, his rifle ran perfectly and we got it sighted in. I instead shot the Ammo Inc stuff through my pistol with it's new H-1 buffer and while it cycled OK ejection was rather inconsistent. Given the rapid rate the company expanded in 2020 I should not really be surprised.

    I would like to thank everyone for their suggestions and will keep them in mind if we have further problems.

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