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Thread: FA FCG in SA lower

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    FA FCG in SA lower

    this is not a question on making any gun fullauto

    what i need to know is i have a FA FCG w/o autosear and a lower milled for SA(as in no room for sear etc)
    can i install the FA FCG in the SA lower and just run normally and what will happen if selector is set on FA? will the disconnector catch the hammer as usual and just work as semi or will it cause some malfunction?

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    Quote Originally Posted by kajen View Post
    this is not a question on making any gun fullauto

    what i need to know is i have a FA FCG w/o autosear and a lower milled for SA(as in no room for sear etc)
    can i install the FA FCG in the SA lower and just run normally and what will happen if selector is set on FA? will the disconnector catch the hammer as usual and just work as semi or will it cause some malfunction?
    They make three position AR15 selectors Safe/Fire/Safe if you want the ability to flip the switch to that happy position legally.
    Why do the loudest do the least?

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    hey thanks for the answer

    its not a legality thing since im not in the US so US Fa laws dont apply

    but i want to assemble an ar today for some nightshooting with some friends tonight ..

    but i only have semi lowers and fullauto FCG so the question is will it work as a normal semi fcg or will it malfunction if it ends up in the sprayandpray position

    my thought is that w/o the autosear the disconnector will catch the hammer as it does in semipos. i might be wrong?
    Last edited by kajen; 04-10-12 at 07:21.

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    Quote Originally Posted by kajen View Post
    hey thanks for the answer

    its not a legality thing since im not in the US so US Fa laws dont apply

    but i want to assemble an ar today for some nightshooting with some friends tonight ..

    but i only have semi lowers and fullauto FCG so the question is will it work as a normal semi fcg or will it malfunction if it ends up in the sprayandpray position

    my thought is that w/o the autosear the disconnector will catch the hammer as it does in semipos. i might be wrong?
    No, the hammer will follow the bolt down, which may pop off an extra shot or two but more likely will just cause a malfunction. ETA: it will work fine in semi.
    Last edited by QuietShootr; 04-10-12 at 08:30.

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    In semi, the disconnect catches the hammer.

    In FA the disconnect tail is shoved down by the selector lever which takes it completely out of the picture.
    At the same time the auto sear rotates into a position that allows it to catch the hook on the outer tail of the hammer where its held back til the carrier coming into battery releases it to fire the next round.
    (or its caught by the trigger if its been released thus stopping the fire cycle until the next trigger pull)

    If you've a FA FCG -sear you may inadverantly end up with a slam fire situation depending on a few variables.

    Now if the tail of the disconnect were ground off to give it a shape like a SA disconnect, the would be nothing for the selector to engage and move and as such should only allow fire in a SA fashion.
    (even if the auto sear was present and functional. with trigger held sear would catch hammer, BCG would release hammer when coming forward. From there the disconnect would catch hammer if the trigger was held down, or the trigger proper would if its released)

    Basically you'd end up with 'safe' 'semi' 'semi' as selections.

    You can see the tail that needs to go. Or just try to obtain an actual SA diconnect.
    Last edited by GTifosi; 04-10-12 at 08:56. Reason: more clearer words

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    thanK you!! that cleared it up 100%

    its just a temporary solution for tonight but i will file it down ..

    thanks again

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    If you install a real fire control group (hammer, trigger, disconnector, selector lever, etc...) minus the auto sear your weapon will fire more than one round. In fact it will fire like a machine gun.

    One thing that can affect this is the type of ammo and primers.



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    Removing the disconnector tail prevents that by allowing it to engage regardless of selector being in semi or auto postion.

    I do contest the 'firing like a machinegun' part though.
    Countless people have removed thier SA disconnector, which creates the same outcome as sear removal; a free flying hammer, in an effort to achive just that effect and found they were wasting thier time and effort.

    Certainly primers have much to do with it, as do a few other things but in general the odds are pretty slim that a slamfire FA will be created.

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    Last edited by GTifosi; 04-10-12 at 11:05.

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    Quote Originally Posted by Iraqgunz View Post
    If you install a real fire control group (hammer, trigger, disconnector, selector lever, etc...) minus the auto sear your weapon will fire more than one round. In fact it will fire like a machine gun.

    One thing that can affect this is the type of ammo and primers.
    That was what I was addressing with my post. As you know it's a hammer following situation as opposed to a properly timed sear release. IME (at a licensed manufacturer, of course) this will not reliably fire automatically, though it's good enough to get you in trouble with the law if that is applicable. Using soft pistol primers is ATF's favorite trick to get a hammer-following gun to fire more than one round for purposes of prosecution.

    Anyway - It won't work well, was my point.

  10. #10
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    I did some testing on this subject and was able to successfully fire several 30 round magazines on full auto. The suppressor seemed to assist in facilitating it.

    I believe some of the ammo was PMC Bronze Line and some handloads.

    Quote Originally Posted by QuietShootr View Post
    That was what I was addressing with my post. As you know it's a hammer following situation as opposed to a properly timed sear release. IME (at a licensed manufacturer, of course) this will not reliably fire automatically, though it's good enough to get you in trouble with the law if that is applicable. Using soft pistol primers is ATF's favorite trick to get a hammer-following gun to fire more than one round for purposes of prosecution.

    Anyway - It won't work well, was my point.



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