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Thread: AR 9 problems

  1. #1
    Boolit Master
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    AR 9 problems

    I am having trouble with my AR9 not resetting the trigger. When i fire a round. the spent case is successfully being ejected and the next round is picked up and fed into the chamber. But the trigger was not reset to the hammer. So the gun cannot fire again. If I then pull the charging handle fully to the rear you can see and feel the trigger engage the hammer. An the gun will fire when the BCG comes forward into battery.
    When I took the rifle in doors to slowly work the action by hand. I found out that the trigger always engaged the hammer when the BCG was pulled to the rear about twice the length of a 9mm round.
    Because of the trigger always resetting by hand at the same spot when the BCG was pulled rearward. I am thinking my reloads don't have enough power to push the BCG back far enough to make the trigger/ hammer function as normally. But the loads i was testing with today were heavier than what i need to function my S&W M&P 2.0 or my High Point 9mm Carbine.
    The load I was testing today was a NOE 124 gr. TC PC using 50%WW/ 50%Soft = Unique powder starting at 4.2 gr which stove piped all fired rounds. At 4.4 and 4.6 of powder all rounds ejected properly and fed the next round but didn't reset the trigger. The book I was looking at had 5 gr. as a Max load. Tomorrow I am going to try 4.8 and maybe 5 if no pressure signs show up
    I also have Promo (red dot) and BE to work with. And in bullets I have a 90 gr RN and a 135ish Round Flat top bullet Kevin

  2. #2
    Boolit Master
    Plate plinker's Avatar
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    Mine does that as well. You need more powerful loads, at least that’s what a AR guru told me. I agree because my hotter loads for another platform function flawlessly. I was getting 2,3 and 4 rounds with one pull of the trigger.

    The guru said it’s a design flaw in the AR9 platform.

    Btw I’m using Odin works barrel, bolt and adjustable buffer.
    Last edited by Plate plinker; 01-19-2022 at 09:11 PM.

  3. #3
    Boolit Master
    Sig556r's Avatar
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    Seems not a shortstroking issue as it picks up the next round. If you assembled your lower, double check trigger assembly if it functions without the upper.
    I only load subs on mine & runs flawless with or without can.
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  4. #4
    Boolit Master Moleman-'s Avatar
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    Might try a lighter buffer, otherwise if it's picking up the next round it's close to being powerful enough to cock the hammer also. What will cycle my 9mm handguns won't always cycle my 9mm blowbacks expecially the ones with the heavy buffer. Sort of the opposite when you put a can on them. The blowback guns work easier and the pistols take a little more powder to unlock with the heavy suppressor hanging off of them even with the neilson device.

    I'm guessing you have a ramped bolt and are using a standard hammer. If so, take a look at the ramp. The bolt has to come back past the end of the ramp where it pushes down the hammer in order to cock it.

  5. #5
    Boolit Grand Master

    Winger Ed.'s Avatar
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    I had that happen with my old SP1.

    Its first problem was that it'd do a 3-4 shot burst every 2nd. or third time I fired it.
    I put in a new fresh trigger spring and fixed that.
    The old one didn't push the trigger back up fast or hard enough to catch the hammer.

    Next I wanted some reduced rounds.
    They weren't strong enough to push the carrier back quite far enough to lock the bolt open on the last round.
    I got some el cheapo buffer springs to carve on.
    After cutting two inches or so off on one, it fixed that problem.
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  6. #6
    Boolit Buddy
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    X2, Try the upper on another lower.

    Ive had similar troubles in a marlin model 60, and a 1911. Ended up being the sear engagements were worn and woudnt catch under recoil.

  7. #7
    Boolit Master
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    Buffer? Bolt group and buffer should be somewhere between 18-21 oz. IIRC. Aftermarket Heavy buffer and the .700" added length may require full power and a can for enough oomph. I run an H3 with added spacer and a can on a Stern setup with commercial cheap fodder with no issues. Blowback designs requires the making of Mr. Newtons #3 happy!

  8. #8
    Boolit Master
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    Is the buffer marked as to what weight it is? Can I weigh the buffer on a scale?
    Where would i go to get a lighter weight buffer?

  9. #9
    Boolit Master
    Plate plinker's Avatar
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    Odinworks has the adjustable for $54.00?

  10. #10
    Boolit Master
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    There are buffers made specifically for AR uppers that are longer than a standard AR buffer and heavier. Yes you can weigh it and some are in the 7-8 oz. zone. A standard AR H3 runs around 5.3-5.4. If standard AR buffer is used I would highly recommend installing a spacer as to keep from beating the bolt stop out of lower.

  11. #11
    Boolit Master Moleman-'s Avatar
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    Other guys brought up a good point, is it only doing this with the reloads and was it working fine before? There are several things like a bad disconnector, weak or upsidedown disconnector spring ect that can also cause this issue.

    For the buffer, if they're not marked you can weigh them. Generally unless you use a suppressor about 5.5 ounces is normal for 9mm. With a suppressor they can easily go up to 11+ ounces. I made mine and they're around 8 ounces which seems to work well for keeping gas away from the shooter although they won't cycle as light of rounds as a standard H2 or H3 buffer will.

  12. #12
    Boolit Master
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    I am feeling so EMBARASED! I worked on the firing mechanism the other day and i neglected to put the disconnector back into the trigger. I properly put ALL of the components back into the lower and everything is working great. 2 slow mag dumps and not a malfunction.
    THANK ALL OF YOU so much for coming to my assistance! What would I do without a group of guys like you to help solve a problem. Kevin

  13. #13
    Boolit Master Moleman-'s Avatar
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    Glad it was an easy one to figure out.

  14. #14
    Boolit Master
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    The extra heavy bolt in a blow back 9mm can cause issues with the FCG. I was using boron coated 2 stage match triggers in mine but switched back to standard bits because it would double and triple fire.
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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check