Target Sports

Need help bolt hold open after last round

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  • Red

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    Hi all,
    So for my latest build I am running a SS 223 wylde barrel, low pro gas block, nickel boron bcg M16 type. So I had been running a lighter buffer and spring and was getting a failure to eject every few rounds using 62gr. I replaced the buffer and spring with a milspec H marked buffer and milspec spring and now she runs 223 55gr and 556 62gr flawlessly. No problems no matter how fast I pull the trigger. Now the problem I am getting is that the bolt wont hold open after the last round fired about half the time. I dont know if maybe I need to just put a few more rounds thru her and the spring will lighten up, or maybe I should cut a coil off the spring. My thinking is that though it has enough gas to cycle new rounds, it may not have just that little bit more to lock it back after the last one. Has to be in the buffer and spring combo since I had tried 3 different BCGs when I had the failure to eject and the only thing that made it reliable was changing out the buffer and spring to milspec.
    Any thoughts? I am thinking cutting 1 coil off the spring and seeing if that helps. It doesnt lock back about 50/50. I dont think a H2 buffer will help but could be mistaken. Not sure.
    Thanks in advance.
     

    wildrider666

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    Basics first. If the bolt face is coming back far enough to pick up rounds, the carrier comes back far enough to be stopped by the bolt catch. Check: the bolt catch/spring are clean and not binding (if slow, bolt will cycle before it can engage), a dirty mag, follower or weak spring: binding or slow, too weak to move bolt catch into position fast enough. IMHO
     

    Red

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    Thanks jj, but I wont be able to get out your way this weekend. Wouldve been sweet to stretch out my new Sig red dot on that 200m tgt too.
     

    Red

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    I upgraded the mag release and same problem as before. Pretty sure it has to be spring and buffer issue. I cut 1 coil and same thing. Cut another coil and it got worse. Only happens with Tula 55gr. 62gr brass stuff it locks back every time
     

    madeSICC88

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    Do you have any other complete rifles or a friend that would let you use one? I would swap uppers on them and see what rifle has the malfunction. Then you'll know for sure what half is the issue. IMO
    Do you have any way to measure the gas port on the barrel?

    Sent from my Nexus 6P using Tapatalk
     
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    Red

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    Yeah I have tried different uppers and BCG. I have it narrowed down to the buffer and spring combo. Went from light buffer which caused empty cases to get caught prior to ejection cause it was cycling too fast. Went to H buffer and carbine spring and no more malfunctions just failure to lock back on Tula ammo, like the Tula doesnt have enough oompf to lock it back after the last round but cycles 100% Locks back fine with 62gr 5.56 no prob, so just need a little tweaking with the spring or buffer to get it lock back for both Tula and 5.56 hotter loads.
     

    16gauge

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    Check the outside diameter on the Tula cases compared to the brass cases. Sometimes the steel cases are a little fatter and stick just enough on retraction to slow down the bolt enough to cause problems. They should work if you don't have any feed issues so just thinking on the dumb stuff. Hope you get it figured out.
     

    Red

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    Yeah I'm gonna get a buffer spring tuner pack and if that doesn't work, then I'm gonna try an H2 buffer. I cut 2 coils off the stock carbine spring and it made it worse. It used to lock at least half the time with Tula. Now not at all with Tula. Still fine with hotter ammo though. Runs like a champ just want it to lock back like it should with all sorts of ammo.
     

    madeSICC88

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    KAK sells a buffer weight kit that might be of some use to you if you really need to dial it in.

    Sent from my Nexus 6P using Tapatalk
     

    Luv2Hunt

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    Two ideas from my 7.62x39 build....I read an article where undergassing was a problem with the bolt locking back or not picking up a round...could the gas port in the barrel be partially blocked? The link is http://www.alloutdoor.com/2014/11/25/making-ar-15-7-62x39-work-reliably/
    second issue I personally had was that I bought a lower kit that was problematic ( I think it was armscor sp?). The bolt release would hold the bolt open but the slightest movement of the upper or lower would allow the bolt to release so I replaced it with a seekins bolt release and it holds the bolt open much better now...... food for thought anyway...
     
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