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AR-15 compatibility question

Discussion in 'Handguns' started by FLbeachbum, Sep 3, 2017.

  1. FLbeachbum

    FLbeachbum Loaded Pockets

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    I shoot the Colt 6920 at work and love it except for the horrible fixed stock. I have wanted an AR of my own for some time now. I know of people who have built their own with parts from several different companies so I'm going to assume they're all pretty much compatible.

    Without going into a long story here, the real question is is there any reason why the upper receiver and bolt carrier from a Rock River Arms FES Predator would not be compatible with a Colt CE2000?
     
  2. les snyder

    les snyder Loaded Pockets

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    I'm not that familiar with the Colt model numbers... does the lower have a standard .250" front hinge pin?... if so, they should be compatible... my older A2 had the off set front pin, and was replaced after I sheared off the third pin... if possible get a mid length gas system with the RRA... I use RRA NM triggers in all my competition rifles... I actually prefer the fixed A1 (VietNam era) stock :)
     
  3. FLbeachbum

    FLbeachbum Loaded Pockets

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    Thanks for the reply. I have no idea about the hinge pin. That is beyond my level of knowledge. I looked at the specs on both companies web sites but couldn't find anything about them. Where would I go to find out?

    For what it's worth, the 6920 is basically the law enforcement rifle and the CE 2000 seems to be the basic entry level rifle marketed as the Expanse M4. I have short arms and the fixed stock makes it uncomfortable to hold. So I cheat often since the work rifles have red dot sites. I'm afraid I'm creating bad habits since I'm not really aiming or even holding it correctly.
     
  4. les snyder

    les snyder Loaded Pockets

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    if the hinge pin is one piece you have the .250" ... most all receivers (except the older Colts) and uppers mate with a pair of .250" diameter captured push out pins... the Colt offset has a straight screwdriver slot one side and threaded boss on other side...I believe the intent was to distinguish the military from civilian versions of the Colts for PR reasons
     
  5. HardToHandle

    HardToHandle Loaded Pockets

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    The parts are probably compatible, but the Colt CE and Rock Rivers are both lower end of the price spectrum. They may have some non-Milspec sizing or components that may not interchange.

    CE is more of a licensed use of the Colt name and not really the same as a legit 6920. The base 6920 will be built mostly to Milspec (code for the Military Specification Technical Data Package) but many lower priced manufacturers/assemblers use non standard materials or different than proscribed assembly techniques. That said, most components since the expiration of the Assault Weapon Ban interchange.

    I own a non-CE, real Colt 6720 skinny barrel upper that goes perfect on my 2003 Rock River lower, so the reverse to your query works for me. I have mixed 5.56mm uppers and lowers from seven or eight different manufacturers with no major issues. The finishes do not match, but they all go bang. As Les mentioned, Colt had some ban-years big pin lowers and uppers in the 1990s but I don't think they made any 6920s or CE models in big pin configuration.

    I would recommend searching on M4Carbine.com for more information. There are some subject matter experts there that know their stuff, but they can be prickly about basic questions.
     
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  6. HardToHandle

    HardToHandle Loaded Pockets

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    I am also with you guys on the shorter A1 stock too. I am shorter of stature and have short arms, so the A1 stock worked better than the 1980's era A2 stock. I always tried to get the mixed rifles - old A1 lowers and the newer A2 uppers in the National Guard - shorter stock but better sights. There is a reason why the US Army and Corps are standardizing on adjustable stocks - people shoot better.

    Today's adjustable stocks have evolved into awesome options. My present go-to stock is the Magpul ACS-L, well worth the coin for comfort and ability to customize.
     
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  7. Telstar

    Telstar Loaded Pockets

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    I don't like to interchange parts but most people generally say that mil-spec is mil-spec and everything else is a crap shoot.
     
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  8. les snyder

    les snyder Loaded Pockets

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    FWIW... my competition AR is a frankengun....A1 stock on Armalite Eagle lower with RRA NM trigger... RRA 16"mid gas with Midwest Industries full float tube, and Miculek comp with M16 bolt carrier, Colt bolt and SOCOM bolt reliability kit....Trijicon TA31F....it has a bunch of rounds since 2005 through it without a glitch...
     
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  9. Mudinyeri

    Mudinyeri Loaded Pockets

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    I build AR's with parts from different manufacturers all the time but agree with @Telstar that one should stick with mil-spec as a standard. Certainly, you can purchase low quality parts manufactured to military (size) specifications but at least they'll fit.
     
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