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Thread: 9mm ar with ramped bolt tested.

  1. #1
    Gunco Addicted for life j427x's Avatar
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    Post1911 9mm ar with ramped bolt tested.

    the mags came in today C-product mags of 32 rounds each.

    so i took the upper out for a quick test.

    i bore sited the 9mm upper to an el-chepo red dot @ 25 meters.

    the upper ain't finished the barrel is just sticking out there no hand guards no front-sight/gas block and so on.

    i fired about 200 rounds of WWB 115gr ammo , had ONE FTE.

    it seems pretty smooth with the ramped bolt. strangely there is SOME recoil not a lot but more than i would have guessed it would have. i was thinking wimpy 9mmx19 got to have no recoil at all--LOL!

    accuracy seems good enough i was slaying tin cans @ 25 , 50 and even 100m with ease.

    it is pretty quiet to me. it sounds like a 22 rim-fire out of this 16" tube. of course my hearing ain't what it once was.

    a couple things i think may have caused the FTE.

    #1 i got the 7.62x39 lower that has the X-power hammer spring installed. this hammer spring might be too much for a 9mm build and is way-way more hammer spring than needed to fire 9mm pistol rounds.


    #2 i just used a stock carbine spring and buffer. i know real 9mm ar-15s have their own buffer set up that is considerably more heavy.

    i may try to cook up one of these heavy 9mm style buffers for this build -- i think the bolt may be wickedly too fast--once it jumps over that wolf XP sprung hammer.

    so far it is an interesting thing to play with.

    the 9mm is certainly worth it if you like "quiet" -- i can see why all the can guys love the 9--

  2. #2
    GuncoHolic BBill's Avatar
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    Hey J4- do you think there's enough recoil to build one and use a Slide-Fire stock?

  3. #3
    gunco irregular moleman's Avatar
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    You may want to weigh your buffer and bolt to see how much they weigh. You should have around 21-22oz or so. The blow backs need the extra weight to keep the bolt closed and slow down the bolt. Without the extra weight the buffer will strike the back side of the buffer tube pretty hard. The heavier buffer will also lessen the felt recoil.

  4. #4
    Gunco Addicted for life j427x's Avatar
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    yea i am way short on the buffer weight.

    i am thinking of making my own buffer. try to get to at least 5oz on the buffer. anybody got a source of good weights?

    i don't think mine is slapping the back of the tube but the bolt is rebounding way too fast.

    BBill i don't know if it has enough recoil as i don't know how much it required to do a slam-fire. my suspicion is that it probably has enough recoil for that.

    i would check around first and see if there is anybody running a 9mm with a slammer attached.

    it is an interesting piece --very quiet in operation --even without a can!

  5. #5
    aka: SDK1968 dutigaf's Avatar
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    j4: did you try just making one of the regular buffers heavier?

    Moleman already knows from some other builds in 9mm blowback that the ideal weight for 9mm with the travel distance you have is 19-22oz of TOTAL combined bolt carrier/buffer weight on a 16" barrel with standard loads..

    if you have the 22oz mark & a regular AR spring that bolt should NOT be able to drive that thing back too far and at 22oz unless you are really smooth running it may even have trouble cycling...

    an ounce changes a lot in one of these.

    sdk
    say what you mean & mean what you say


  6. #6
    THE 9mm ADDICT MUSIBIKE's Avatar
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    RRA sells a buffer that drops right in and works great.
    M U S I B I K E

  7. #7
    Gunco Addicted for life j427x's Avatar
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    no i haven't had time to fool around with the buffer yet.

    i am going to go shopping at the hardware store and possibly wall-words fishing weights.

    i will come up with a low buck solution.

  8. #8
    Gunco Addicted for life j427x's Avatar
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    just got through testing my lead-heavy 9mm buffer. it seems that 4oz of fishing weights pressed into the CAR buffer is enough weight.

    i don't know the total weight i am thinking somewhere around 4.5 to a bit over 5 oz.


    was a snap to do with the 80 ton press. just rolled out the 1oz sinkers till they would fit in the tube then pressed them in with the press. the last weight sticks out the buffer slightly for an even 4 oz of lead--

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