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M16A1 and A2 - small differences in receiver details?

Discussion in 'Rifle Country' started by AirPower, Mar 24, 2005.

  1. AirPower

    AirPower New Member

    I'm trying to put together a couple of "representative" M16 models, namely A1 and A2. Here is what I have so far. The A2 is all Bushmaster with A2 barrel so it's pretty close to real thing. The problem I have is finding an authentic A1 lower, does anyone make those any more. And what's the difference between A1 and A2 lower? I did get the Colt upper that has forward assist but no shell deflector. Anything else I should change to make it close to A1 spec?

  2. Trebor

    Trebor New Member

    The M-16A1 did not have the "fence" around the mag release. Off the top off my head, I can't think of any other difference in the lower.

    You could also build up a M-16 (no-A) replica. Find a SP1 upper without the forward assist. You'd also need a 3 prong flash hider.
  3. Harry Tuttle

    Harry Tuttle New Member

  4. vanfunk

    vanfunk New Member

    Actually, the M-16A1 did have the fence around the magazine release, but did not have the extra reinforcements at the rear detent pin and receiver extension area. Only the early M-16 variants (Colt 601, 602, etc) had slab-sided lower receivers. Many M-16's were upgraded to A1 status by putting A1 uppers on older lowers, though. Colt continued to manufacture commercial AR-15's with slab-sided lowers up through 1991, though. I have a '91 production rifle rollmarked "AR-15 A2 Government Model" that has a typical A2 20" government weight upper atop a slab-sided lower.

    Your M-16A1 clone is pretty close - you've got a genuine M-16A1 upper on an A2 lower. The only way you'd get it closer to spec would be to have a skilled metalsmith remove the reinforcements from the rear of the receiver and have it reanodized (not cheap). There's a guy over on www.ar15.com who is gearing up to produce true A1 receivers again, and it seems that the demand is there for a limited run. Also, it looks like you've got a chromed bolt carrier in there, too. You'd want to swap that out for a parkerized one to be authentic. The chromed carriers were long gone by the time the A1 came out.

  5. Kharn

    Kharn New Member

    I believe Colt had done a large run of slab-sided forgings, but then the .mil said it needed the fence for the A1 variant. Colt, not wanting to waste anything and being stuck with a large supply of slab-sides, sold them to civilians.

  6. Bartholomew Roberts

    Bartholomew Roberts Moderator Emeritus

    Actually military M16A1s do have the fence around the magazine release button and have had them since the 70s. The SP1 does not have a fence around the mag release button and neither did the original XM16E1. You can see the differences here:


    The only other difference I can think of between the A1 and A2 lower receivers is that the A2 has a slightly thicker extension where the buffer tube screws in compared to the A1. However, it is one of those differences that you pretty much have to see side-by-side to notice.

    Looks like you have done a pretty good job on them both! Is the barrel on the A1 an 1/12?
  7. AirPower

    AirPower New Member

    Thanks for the info. so the chromed bc is a no no for A1? I thought it was used for a period of time during 'Nam. And right now it has the A1 flash hider with the bottom slot (where as A2 didn't have bottom slot), but would the 3 prong be right also? I just thought the 3 prong was more unique looking.

    The skinny barre is in 1/12 twist, but it's not Colt (though the entire upper was originally assembled that way I believe). It is a SAKO Defense barrel, stamped "chromed bore". Does that mean it's chrome lined barrel, or just the chamber itself? And was Sako Defense a legit contractor for the US Govt?

    The lower is an RRA A2 and I still need to find a good grip, somehow this grip doesn't look right for the profile, does anyone have an older A1 type grip?
  8. vanfunk

    vanfunk New Member

    A "fresh off the assembly line" circa 1968-69 Colt M-16A1 would have the following features:
    Birdcage flash suppressor
    A1 upper with forward assist
    parkerized, chrome lined (but not fully chromed) bolt carrier
    1/12" A1 barrel, chrome chamber (and likely chrome bore)
    A1 lower with mag fence
    A1 pistol grip, no finger groove

    Fully chromed carriers and three-pronged flash suppressors were standard on early M16's. Chromed carriers were replaced with chrome-lined carriers starting in '65-'66, IIRC. 3-pronged hiders were phased out '68-'69. Exceptions are the rule, however, so I suppose it's possible to imagine grunts toting M-16A1's in '71 or so that had chromed carriers and 3-pronged hiders (prolly some "duckbills" floating around too).

    Your SACO Defense barrel is USGI. Those are great barrels, BTW. It is fully chrome lined, chamber and bore.

    Have fun!
  9. vanfunk

    vanfunk New Member

  10. Trebor

    Trebor New Member

    There's some *REALLY OLD* M-16 lowers still in the inventory. I used an M-16A2 at the Small Arms Firing School last summer that was marked "COLT AR-15" on the mag well. It was also overstamped "M-16A2" over an older "A1" marking. Almost all the rifles I looked at closely on the line were originally "A1's" rebuilt to "A2" standard. There was at least one other rifle marked "AR-15" as well.

    BTW, thanks everyone for the correct on the mag fence. I'm not an expert on the M-16 by any stretch and was probably thinking of the civvie AR variations.
  11. AirPower

    AirPower New Member

    For the most part, my project is done, I have original Colt M16A1 stock parts on the A1, also 20rd mag looks great for the nostalgic feeling.


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