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AR Question

Discussion in 'Firearms' started by Seacowboys, Aug 5, 2015.

  1. Seacowboys

    Seacowboys Senior Member Founding Member

    I just put together a pistol configured AR-15 built on a Bushy Lower and a Spikes upper with a 11.5" barrel. The weapon essentially fires as a single shot repeater, i.e., it fires the chambered round, ejects the spent round, resets the hammer, sear and disconnect but fails to pick up the new round out of the magazine. If it resets the trigger and ejects the round, it probably isn't short-stroking so it must be cycling too fast to allow the next round to jump into place. The "Experts" on Arf.com are so full of shit, that I don't know what to believe. They say to bore out the gas port one size to allow more gas but this doesn't make any sense if the weapon is cycling too fast...more gas, faster cycle? The other half of the ARFsperts say to use a longer gas-tube assembly wrapped inside the handguards to reduce the amount of gas to the weapon.The other option seems to be to try a heavier or lighter Buffer and spring, a point that about half the ARFsperts support either one or the other of. I have the same configuration on one of my M16 rifles that functions well with a suppressor but has the same failure when fired without the suppressor, though it always functions with a .22 conversion kit, regardless of suppressed or not. Anyone have this same problem that they have personally resolved?
  2. kckndrgn

    kckndrgn Moderator Moderator Founding Member

    Never had the problem but it does sound to me like the bolt is not going back far enough to pickup the next round from the magazine.
    Something to try that may prove/disprove this. With an empty gun (no magazine, no rounds, double check, check again :) ) Pull the trigger to dry fire the weapon, then using the charging handle pull it back in small increments to see how far back it needs to go to reset the trigger and or eject an empty casing. Now that you have that distance, you put a magazine in with a snap cap or dummy round and pull the charging handle back to the distance you checked. Is it back far enough to pick up a round? I'm thinking it's not, but I may be wrong.

    If the bolt is not going back far enough either not enough gas is coming through the gas port, or you need a lighter recoil spring.
    I also think more gas would make for a longer cycle time, why? because it will push the bolt farther back, more distance to travel, longer cycle time.

    Good luck
    Dont likes this.
  3. HK_User

    HK_User A Productive Monkey is a Happy Monkey Site Supporter

    What loads have you tried with this rig?
    It would seem that the suppressor is allowing more back pressure/longer duration to the bolt bleed system, so no suppressor and the gas escapes faster out the bore and the cycle time changes.

    Not all barrels are ported to a Mil Spec and the shorter barrel can change the cycle time/length of "push" of the bolt.

    Short cycling is common with my 300 using softer loads/subsonic loads without a suppressor.

    An adjustable bleed valve is the problem solver for me.
  4. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    While I've not had the problem, I can see a couple points worth checking.
    -Possible short stroking enough that the next round is not picking up, even tho' the trigger reset is done Reset does happen before the bolt clears the top of the mag. Like Ryan says, the fix is more gas thru the port (drilling is a permanent fix, if it doesn't work, it's a new barrel time) OR lighter recoil spring.
    -Magazine lip problems. Knowing you, you've already tried different mags. If not, do so. If necessary, sacrifice a mag by opening up the lips a tad to let the round come a teensie bit higher.
    -Limp wristing. The AR platform needs resistance on firing.
    -Enough lube? ARs like to be wet. (BYKT)
    -Enough breakin rounds up the pipe?
    -Try a snortier load, might help if short stroking is happening.

    My money is on a mag problem. As standardized as ARs have become, it doesn't take much of tolerance stacking between one mfr's upper and another's lower that problems could happen. Falling back on a mix and match for defense does NOT sit well with me, or at least not until a thousand or so trouble free rounds have been launched. If it is a mag problem, you might wind up with a set of non-standard mags dedicated to this one gun. Not fond of that either, but for a fun gun that is not setting by the door, so to say, it might be acceptable.
  5. Seacowboys

    Seacowboys Senior Member Founding Member

    The adjustable gas-block seems the most logical solution to me, after making the port a size or two larger. I have tried a variety of ammo, Win white-box, steel cased romy crap, lakecity and have tried numerous mags. Also tried a couple different buffers and springs. Plenty lube and I haven't limp-wristed a weapon since I started shooting 1911s at the age of six.
  6. Seacowboys

    Seacowboys Senior Member Founding Member

    Most the Arfsperts seem to think it is a cycling too fast thing caused by the shorter gas-tube, so it would seem that if I restrict the amount of gas by installing an adjustable gas-block and this doesn't solve the problem, then I open it back up and drill the gas port.
  7. melbo

    melbo Hunter Gatherer Administrator Founding Member

    A friend had to install a full length gas tube to correct some cycle issues on a 11.5" although I never asked about what the issues were. It looked similar to this one:
  8. Seacowboys

    Seacowboys Senior Member Founding Member

    I have seen that done, Melbo.
  9. HK_User

    HK_User A Productive Monkey is a Happy Monkey Site Supporter

    Dwell time and volume, I like it.
    sec_monkey likes this.
  10. HK_User

    HK_User A Productive Monkey is a Happy Monkey Site Supporter

    If you add the adjustable gas port then you need to open up the port first.

    Logic says you need more volume.

    Your Logic May Vary.
    Ganado and melbo like this.
  11. Seacowboys

    Seacowboys Senior Member Founding Member

    I should be able to determine if it is short-stroking by placing one round in a mag and firing to see if the bolt locks back.
    Tully Mars likes this.
  12. tacmotusn

    tacmotusn Mosquito Sailor

    my 7.5 inch barreled ar 5.56 upper works fine with carbine M4 configuration tube/spring/buffer, and all loads tried so far. only test fired and disassembled as pistol lower is yet to be built for it. have components but have not taken time to finish it.
  13. Seacowboys

    Seacowboys Senior Member Founding Member

    Just determined that it is probably a short-stroke by firing with a single round in the mag and though it ejected and reset trigger, did not lock open.
    Dont likes this.
  14. Quigley_Sharps

    Quigley_Sharps The Badministrator Administrator Founding Member

    Tully Mars and sec_monkey like this.
  15. Seacowboys

    Seacowboys Senior Member Founding Member

    I think I will swap the M16 BCG out with an AR-15, it's lighter
  16. gunbartender

    gunbartender Monkey+

    Is it a factory built spikes upper, or one you built?

    If it's factory, try calling spikes.
  17. Witch Doctor 01

    Witch Doctor 01 Mojo Maker

    I was thinking buffer spring... with a need for a Carbine rated spring vs. a normal AR spring buffer set up...

    WMMV (Weapons mileage may very...)
    Tully Mars likes this.
  18. Grand58742

    Grand58742 Monkey+++

    Try a heavier buffer before you mess with the gas system. Try an H2.
  19. Grand58742

    Grand58742 Monkey+++

    The problem is your actions are too light. Your bolt carrier is cycling too fast before the mag can catch up. Which is why you aren't picking up the next round.
  20. Seacowboys

    Seacowboys Senior Member Founding Member

    Tried an A2 buffer and a M16 bolt carrier, that's as much weight as I can add, still doesn't cycle.
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