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Stupid question on AR's

Discussion in 'Rifle Country' started by glenjoy, Jul 17, 2009.

  1. glenjoy

    glenjoy member

    Aug 28, 2008
    I would like to ask, what are the mechanical/functional differences of an AR (fire and safe) and an M4 (full, semi, safe)?

    What I mean here are the parts where they differ, thank you.
  2. bkjeffrey

    bkjeffrey Active Member

    Aug 12, 2007
    Southern states
    I believe M4 is a generic term that covers any AR15/M16 rifle that has a 16.5" shorter bbl and a collapsable stock. The difference is the term AR15 or M16. An M16 is a class 3 firearm and an AR15 is semi auto.

    Basically, the only operation parts that the AR and M16 have in common is the upper reciever. The Lower reciever of a M16 is milled to accept a sear and drilled to allow for a sear pin. The safety / selector switch is different between the two, as well as the trigger and disconnect. The hammer is different also. None of the lower reciever parts are interchangeable. The M16 also uses a slightly different bolt carrier. It is milled slightly differently than an AR15 carrier because it has to engage the sear properly. An AR15 bolt carrier cannot be used in an M16.

    You can search the web for ar15 and M16 schematics the see the differences in the parts. Burst fire is a whole other animal, it uses burst cams and all kinds of parts different from the standard M16.

    Google will provide you with all the answers you seek as well as the legalities of the issue.
  3. c5_nc

    c5_nc Member

    Dec 11, 2008
    If it was before 1986 and needed to do a FA conversion you would need these parts, if you were a licenced manufactor today you would need the same:
    H-H3 or other heavy Buffer - Depending on barrel length, gas system
    M16 bolt Carrier - Rest of BCG parts are the same but you need it to trip disconnector
    Fire Control group - I believe these will physicaly fit in a ar-15 lower but would keep shooting until mag is empty, even if you lifted off of trigger if it worked. Likely you would get hammer following bolt back you would just get a light primer strike on the 2nd round and have to recock
    Auto Sear - ar-15 has to drilled for install, also a lot of material removed from the lower, the drill points would have to be "perfect". On a M4/M16 this is just different part from the factory.
  4. KW

    KW Member

    Nov 20, 2003
  5. praharin

    praharin Member

    Feb 10, 2006
    The M4 (and its variants, such as the M4A1) is the shorter version of the M16. it has a 14.5" barrel, and usually 3rd burst or a FA trigger group. It is not a generic term. Wiki "M4 Carbine" if you don't believe me.
  6. Runningman

    Runningman Participating Member

    Dec 10, 2008
    :banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead: :cuss:

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