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What makes an AR-15 shoot full auto?

Discussion in 'Rifle Country' started by peck1234, May 31, 2008.

  1. peck1234

    peck1234 Well-Known Member

    Just wondering what part of an AR-15 will make it shoot on full auto? Is it a certain lower?, Bolt?
  2. Glockman17366

    Glockman17366 Well-Known Member

    Just do a search on the web...
    The AR-15 is a fine sporting rifle. Modifying a rifle or any other firearm is a federal offense (although I'm not sure of the constitutionalty of those laws).
    The parts required won't fit in an unmodified semi-auto AR-15, to the best of my knowledge.
  3. taliv

    taliv Moderator

    the hammer, bolt carrier, disconnector and selector switch are all different from the semi-auto parts, and there is another auto-sear doohickey in there.
  4. theotherwaldo

    theotherwaldo Well-Known Member

    Discussing this in public can get you some unwanted attention.
  5. briansmithwins

    briansmithwins Well-Known Member

    About $15k to $17k, assuming your state allows it.

    Can't do conversion unless you're a licensed manufacturer. Violations are a major Federal no-no, which are aggressively prosecuted.

  6. MaterDei

    MaterDei Well-Known Member

    The OP didn't suggest at all that he was wanting to illegally modify his existing semi-auto firearm. When we firearm enthusiasts make such a big deal about somebody curious about how a gun functions, we're not doing ourselves a favor.

    Calm down people and if you don't know the answer to his legitimate question just move along.

    /rant off
  7. redneck2

    redneck2 Well-Known Member

    So, I guess every time someone asks a question about Class III, they'd better expect a knock on the door....

    oh CRAP....I just looked out the door.....here come the Feds...

  8. peck1234

    peck1234 Well-Known Member

    thanks MaterDei Just like to know how things work you know?

    All beacause i like to see how nuclear bombs work and how there made doesent mean im going to make one! : )
  9. nalioth

    nalioth Well-Known Member

    It is unfortunate we are where we are.

    Answering the OPs question can prospectively land one in trouble.

    I don't see any 'favors' being done or denied.

    To the OP: As mentioned above, there are plenty of sites on the web which go into this.
  10. Telperion

    Telperion Well-Known Member

  11. DWARREN123

    DWARREN123 Well-Known Member

    For a semi auto it is either wear and tear or bad gunsmithing. For a Class III it is the fire control system (trigger-sear so on).
    It is illegal to mod a semi unless you have BATFE approval and signed off paperwork.
  12. TexasRifleman

    TexasRifleman Moderator Emeritus

    Ignoring the wailing and gnashing of teeth, it's a fairly straightforward answer.

    The basic answer to your question is that yes, it's a special lower in most cases plus a few extra parts. There is an extra hole in full auto lowers for a pin to hold a sear that does not exist on the semi.

    When the semi fires, the existing sear has a hook that holds the hammer back if the trigger is held down, stopping it from firing again until the trigger is released, or "reset".

    This additional sear on the full autos releases the sear holding back the hammer, allowing it to fire as soon as the bolt is back in "home" position, starting the whole process over again. the trigger remains down and the bolt carrier "fires the gun" from this point on until the trigger is reset again, stopping the process.

    The bolt carrier for the M16 has more metal in a certain spot than the semi's as well, this extra metal is what trips that auto sear to let it know the bolt carrier is "home" again and ready to fire.

    Now, some will say there is a way to do it by just getting that semi sear to "disappear" but that really doesn't make the gun full auto, it makes the hammer follow the bolt forward basically creating an intentional slam fire. This is very dangerous in that on many guns the cartridge can fire before the bolt is locked in place, firing "out of battery". Many times when that happens the shooter loses body parts and the gun shreds itself. That assumes the intentional slam fire even works. Most of the time nothing happens, the hammer follows the bolt too closely and doesn't hit the firing pin hard enough to do anything at all. So, it's a dangerous, illegal, and mostly useless "trick". The loss of body parts should be scarier than prison with the slamfire method :)

    It's not an unreasonable question, and the answer doesn't really give you any info on how to actually perform the conversion so I'm not sure what all the fuss is about.

    If I ask how cars can go 200MPH would there be such panic?
  13. rcmodel

    rcmodel Member in memoriam

    The point of "if you can do it" is moot anyway.

    It has been illegal to modify or manufacture a new civilian machinegun since 1986.

    So, you can't get ATF approval no matter how hard you try, or how much you pay.

  14. Chipperman

    Chipperman Well-Known Member

    The Brady Bunch is not trying to prevent people from building or buying cars that can go 200MPH.
  15. TexasRifleman

    TexasRifleman Moderator Emeritus

    Don't kid yourself. EU wants to ban cars capable of exceeding 101MPH.

    It will hit here next.

    "They" want to protect you from more than those silly guns and knives. You need to be protected from EVERYTHING.

  16. IndianaBoy

    IndianaBoy Well-Known Member

  17. Chipperman

    Chipperman Well-Known Member

    Did you get that out of Shotgun News? :uhoh:

    Even a drop in auto sear by itself will not make the gun full-auto.
  18. TexasRifleman

    TexasRifleman Moderator Emeritus

    If we're posting photos of hacks, here's another.

    I have one of these, all legal like and everything!
    $275 for 2 stamped pieces of sheet metal (in 1984).
    Sadly, and sickeningly, these sell for $8-10k or so now.

    I've heard there were close to 1000 of these things registered but I don't know if that's true or not.

    Takes more than just dropping this thing in that's for damn sure.

    Almost more trouble than it's worth. Takes a pre-89 SP1 Colt to work "drop in" but even then there is a lot of timing stuff to work out.

  19. Chipperman

    Chipperman Well-Known Member

    OK, here's mine:
    The little pin above the selector pin is where the auto-sear lives. A semi-auto AR will not have this hole drilled.
  20. Technically speaking, the answer is: Holding the trigger to the rear, combined with EITHER (a) an auto sear installed (which trips the hammer immediately after the bolt is closed), OR (b) in the case of accidental full-auto, a slam-fire, which is caused by the hammer following the bolt home, which is in turn caused by a missing or "misconfigured/modified" disconnector. Is that your question?

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