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Thread: K-booms with bump fire 9mm ARs--

  1. #1
    Gunco Addicted for life j427x's Avatar
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    Arrow K-booms with bump fire 9mm ARs--

    Anyone tried the Promag 9mm Mag block? With low $$ barrel info and an update with the block...ouch! - Page 3 - AR15.COM


    i think i know what is going on with the bump-fire K-booms on the third page.

    it ain't the mag block either--

    any body else want to give it a go?

  2. #2
    gunco irregular moleman's Avatar
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    ? the pics show a fan and a marlin lever gun where the oob are supposed to be.. There really isn't anything to prevent the firing pin from hitting the primer on the blowback ar15's except the shape of the bolt below the firing pin which isn't ideal.

  3. #3
    Gunco Addicted for life j427x's Avatar
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    there has been some k-booms with the bump firing the 9mm ar-15s.

    i know what the cause and the solution.

    what is causing this is --solid buffers --they cause bolt bounce, and

    weak and or too short a recoil spring.

    over at the mall ninjas the make out like blow-backs just go k-boom ever so often anyway?--i'm thinking--wtf??--LOL!

    if you going to simulate auto fire you better have a strong recoil spring and a real dead blow style buffer. it don't hurt to be over sprung but under spring is s no-no!

    one of my pals built one of these with all colt stuff --that damn thing was blowing the mag out on the ground every third hit and the shell casing would be split all the way back to the rim--like it was a peeled bannana

    guess what? he had one of them solid mall ninja required buffers and a weak and some what short recoil spring on top of that.

    some mall-ninja told him a weak spring would slow the rate of fire and the solid heavy buffer was the in style thing--

    me just being an ass as usual got one of them overly light weight CAR buffers that came out of a china made stock kit, and i did put in one good recoil spring that was the correct length and pressure.

    i was shocked at how well it runs in bump firing --looks a bit fast --like 800rpm too--LOL!

    damn near the real thing. now he tossed that solid buffer in the scrap can anyway.

    it runs like a champ now-- hell i got to get me a bump-fire stock--LOL!

  4. #4
    Gunco Good ole boy tanvil's Avatar
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    J4, any one who reads this should give a cigar.

    This is vital info.

    Thanks for posting it, you saved some ARs from destruction.

  5. #5
    Gunco Addicted for life j427x's Avatar
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    it probably ain't a problem less you bump firing and get the bolt to bounce -

    -these blow-back jobs don't act like a gas operated gun at all with simulated FA/bumpfiring is going on.

    the one i tinkered with only peeled the brass when bump firing -- and it was the third round that open bolt discharged. spit the mag straight into the dirt too--

    i don't get no credit cause the fix was a phone call to a fellow who ran NFA papered full auto UZIs.

    it was he that suggested getting rid of the solid buffer and adding a stronger recoil spring.
    he said ironically FA uzi firing from a closed bolt had a faster cyclic rate with a stronger recoil spring but operated better--

    he said the dead blow action of the buffer was more critical on this type of app than the weight of the buffer--

    i am inclined to think he is correct.

    we test fired it a few times yesterday .

    it just gobbeled up the 9mm --no more open bolt k-booms either.

    it would be a bit of a scare to have one of these things blow burning powder in your face. good luck that my pal only got a ringing ear and some smoking powder in his beard when it went "boom" on him.

    for the first mag or two be damn sure you hold it with the ejection port far away from you face when testing a bump firing solution on a blow-back!

    their pretty nasty when she furbar!

  6. #6
    Citizen, Patriot, Ranger bellson's Avatar
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    Quote Originally Posted by j427x View Post
    it probably ain't a problem less you bump firing and get the bolt to bounce -

    -these blow-back jobs don't act like a gas operated gun at all with simulated FA/bumpfiring is going on.

    the one i tinkered with only peeled the brass when bump firing -- and it was the third round that open bolt discharged. spit the mag straight into the dirt too--

    i don't get no credit cause the fix was a phone call to a fellow who ran NFA papered full auto UZIs.

    it was he that suggested getting rid of the solid buffer and adding a stronger recoil spring.
    he said ironically FA uzi firing from a closed bolt had a faster cyclic rate with a stronger recoil spring but operated better--

    he said the dead blow action of the buffer was more critical on this type of app than the weight of the buffer--

    i am inclined to think he is correct.

    we test fired it a few times yesterday .

    it just gobbeled up the 9mm --no more open bolt k-booms either.

    it would be a bit of a scare to have one of these things blow burning powder in your face. good luck that my pal only got a ringing ear and some smoking powder in his beard when it went "boom" on him.

    for the first mag or two be damn sure you hold it with the ejection port far away from you face when testing a bump firing solution on a blow-back!

    their pretty nasty when she furbar!

    J, you are scaring me!
    Imagine whirled peas

    Peace, Love, And Superior Firepower






    Bellson

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