Stupid question on AR's


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glenjoy
July 17, 2009, 09:24 AM
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.

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bkjeffrey
July 17, 2009, 09:38 AM
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.

c5_nc
July 17, 2009, 10:25 AM
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.

KW
July 17, 2009, 03:12 PM
Check out http://www.quarterbore.com/. Under the AR-15/M-16 stuff are a number of great descriptions and pictures.

praharin
July 17, 2009, 03:39 PM
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.

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.

Runningman
July 17, 2009, 04:11 PM
I believe M4 is a generic term that covers any AR15/M16 rifle that has a 16.5" shorter bbl and a collapsable stock.:banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead::banghead: :cuss:

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