1. Bikerdoc's passing and how you can help

    As many of you know, bikerdoc- AKA Al Spiniello- is no longer with us. There are always extra expenses when someone passes. If you would like to contribute to support his family, please do so here: Bikerdoc GoFundMe page.

    (Note - this notice can be dismissed by clicking on the X in the upper right corner.)
    Dismiss Notice

AR upper.300blk not cycling. Suggestions requested.

Discussion in 'Rifle Country' started by GooseGestapo, Oct 17, 2015.

Thread Status:
Not open for further replies.
  1. GooseGestapo

    GooseGestapo Member

    Joined:
    Jan 6, 2003
    Messages:
    4,839
    I built a "mixmaster" upper from an assortment of used parts as a "plinker", particularly for cast bullets.
    It has a "mid length" gas system, 16" barrel. Not sure, but believe it has a carbine length buffer assembly.
    Even with over book max loads it's not cycling enough to eject, feed, or lock back. Closest I've come to getting it to function is with a 180gr bullet and compressed load of Acc#1680.
    What can I try to get it to work?
     
  2. mavracer

    mavracer Member

    Joined:
    Jan 9, 2007
    Messages:
    5,639
    Location:
    wichita
    I've never seen a mid gassed 300 BO, I suspect that's the problem. You might try opening up the gas port.
    Not sure what powder you're going to use that will be slow enough to have enough gas that far down the barrel and have enough case capacity to get it there.
     
  3. Walkalong

    Walkalong Moderator Staff Member

    Joined:
    Nov 20, 2006
    Messages:
    69,205
    Location:
    Alabama
    I believe mavracer has it.

    Mine is a carbine gas system and I have to use a ar15 carrier instead of a heavier M16 carrier with the rifle buffer in an A2 stock. I could play with the buffer, but it runs great like that. My point is a little more weight in mine and it does what your describing.

    So I would agree that opening the gas port a tee tiny bit is the answer.
     
  4. bikemutt

    bikemutt Member

    Joined:
    Dec 24, 2010
    Messages:
    4,480
    Location:
    Vancouver, WA
    Below is a link you may find handy. I had a similar problem with a 10" Wilson Combat-barreled upper I'd built, even with an adjustable gas block wide open I couldn't get it to cycle reliably. The solution was to open up the gas port to the size recommended in the link for that length barrel and gas system, now it runs like a champ.

    http://micromoa.com/300-blk-port-size-testing/
     
  5. GooseGestapo

    GooseGestapo Member

    Joined:
    Jan 6, 2003
    Messages:
    4,839
    Thanks bike. Wasn't sure there wasn't another fix.
     
  6. OilyPablo

    OilyPablo Member

    Joined:
    Sep 2, 2012
    Messages:
    3,120
    Location:
    WA State (NOT in Seattle)
    Good stuff above. I have learned a lot from the .300 club trying to get my 10mm AR to cycle properly. One thing that I am very certain of in dialing in lightly gassed AR's is all parts must be very free moving. There is little room for lack of lubrication or tight bolts, for example. Make sure your bolt is fairly loose in the carrier. And for sure I recommend this:

    http://www.davidtubb.com/ar15-tubb-parts/ar15-buffer-spring-stainless
     
  7. bikemutt

    bikemutt Member

    Joined:
    Dec 24, 2010
    Messages:
    4,480
    Location:
    Vancouver, WA
    Speaking of Tubb springs and 300 BLK, I have a Rem 700 in 300 BLK where I installed the Tubb Rem 700 Speedlock firing pin and spring. The rifle became a habitual and frustrating light-striker. I ended up keeping the firing pin and replacing the spring with the stock Rem one.

    As far as buffers and springs in ARs go, I'm sold on JP Silent Capture, not cheap, but worth it.
     
  8. OilyPablo

    OilyPablo Member

    Joined:
    Sep 2, 2012
    Messages:
    3,120
    Location:
    WA State (NOT in Seattle)
    Bikemutt not sure what you are implying but I know nothing of the light firing pin spring. Doesn't sound like a good idea and not an AR option. I just know from others the Tubbs AR spring is the real deal for the .300Blk.
     
  9. bikemutt

    bikemutt Member

    Joined:
    Dec 24, 2010
    Messages:
    4,480
    Location:
    Vancouver, WA
    It's not a light spring, it's one that is insufficiently strong to ensure reliable primer ignition, at least with 300 BLK, the result was light strikes. I don't know anything about Tubb's AR buffer springs since I don't use that type of spring in my ARs. I hope it works better than the firing pin spring they sell with their Rem 700 kit.
     
  10. OilyPablo

    OilyPablo Member

    Joined:
    Sep 2, 2012
    Messages:
    3,120
    Location:
    WA State (NOT in Seattle)
    Good way to put it.

    I know for a fact David Tubb's Lightweight Buffer spring for AR-15 is used in .300Blk and pistol caliber lightly gassed AR's with much success. It allowed my 10mm AR to more or less properly cycle, even with a sticky bolt.

    That said, in a midlength gas .300Blk.....the OP will need all the help he can get. As in changing to a carbine barrel and gas tube.
     
  11. bikemutt

    bikemutt Member

    Joined:
    Dec 24, 2010
    Messages:
    4,480
    Location:
    Vancouver, WA
    I've never heard of a 10mm AR, I'll bet that is fun to shoot. Pardon my ignorance but can it shoot .40 cal as well?
     
  12. OilyPablo

    OilyPablo Member

    Joined:
    Sep 2, 2012
    Messages:
    3,120
    Location:
    WA State (NOT in Seattle)
    It's very fun to shoot. Nice moderate round, pistol caliber without all the expense of the bruiser .450-.500 AR rounds.

    No .40S&W - it's only chambered for 10mm. I can shoot light 10mm loads if I want .40S&W type rounds, but that that keeps it on topic as tuning the gas system for a variety of rounds is important to me. By making the bolt free moving, yet well sealed, I can tune with the buffer mass and spring. Maybe someday I will try the captive buffer/spring assemblies. The same should apply to .300Blk and suppressed AR's.
     
Thread Status:
Not open for further replies.
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice