Oh, yeah!
I want to see all kinds of A2s here!

We will have to agree to disagree on this one.  The XM4 and M4 are very different - the barrel, upper receiver, handguards, stock, sights - are major differences.  If you want to say the functioning elemts are similar (BCG, FCG) I agree, but then again, we know that the functioning elements in a M16A2 and M4 are also nearly identical, but that does not mean the weapons are identical.  One thing is for sure, the production of the 6520 preceded the M4.  The XM4 was still just a prototype and was never fielded as a service weapon in the Military or Federal law enforcement (USG).  

Thanks for the good information and history you have provided.  Good thread.

Anything with an A2 upper.  No flat tops.  "C7" uppers are OK since the Brunton Bump was one of the M16A2 features introduced by Colt on their 7XX series of weapons, and used the Canadians on their C7/C8 weapons which were for all intents and purposes a parallel development to the M16A2.

The XM4 prototypes and production M4s had the same stock (fiberlite plastic; the reinforced and other stock types came after the M4 was already in service) and rear sights (the A2 type adjustable for windage and elevation).  The barrel used on the M4 was one of a number of types tested on the XM4.  Colt delivered double shield handguards for testing on the prototype carbines in April 1986.  I would direct you to this to this thread rather than start a whole separate discussion about the existence of fixed carry handle M4s.  I would say that the XM4s were very similar to the production M4s by the end of their testing, just like most prototypes are by the end of their development.

We are thinning out the real disagreements from semantics hehe.

I've always considered an A-2 anything with an A-2 fixed sight, carbine or rifle length.  Seems to be the majority in the voting poll also.

Parts and components are not semantics.  The fact that XM4 and M4 sound similar is semantics.  I will concede the M4 evolved from the XM4, but they are  two very different firearms.  This is often the case in R&D - the final product can bear little resemblence to the original concept.   I'm not starting a separate discussion here, just stating the facts in rebuttal of my original post.  Anyway, back to the A2 discussion.  Again, thanks for the additional information and thread link.

I would accept this, and any other EARLY style M4's that have a fixed carry handle A2 upper and do not have quad rails and etc, as being legitimate "A2"s.

I think the general spirit of the "A2" is a 1990s (maybe early 2000s) style rifle/carbine that has the fixed A2 style carry handle and preferably does NOT have accessory rail systems...
I won't get all huffy and offended, however, if we want to talk about C7 or C8 builds in here, or if we want to talk about the "A2" carbines/rifles that are marked and/or marketed as an "A2" yet have A1 sights/uppers. (IIRC, Colt Model 713 had an A1 upper without brass deflector, A1 barrel, and A1 slipring mounted to an A2 style lower and fitted with A2 handguards)

Apparently, defining an A2 is just as difficult as what Retro means.  It's like they say " If it walks like a duck..... or "I  know it when I see it....
Rails and modern appointments don't cut it IMHO.  YMMV.  It's not about what you can make it into, but rather, what it was meant to be.
Ralph

A2 Upper and lowers...  for the A2 definition IMHO.

It is what it is.. A2 Upper with fixed handle and reinforced A2 lowers.  That about covers it.  The purists will keep them simple with the 1/7 bbls and A2 fixed stocks... but all the kits have 1/9 bbls with all kinds of accessories, and that is fine too..

BTW, I voted "None of the above"...

+1

M16A2s are rifles  not carbines

The 723 and 727 were both called "M16A2 Carbines" by Colt, the 733 the "M16A2 Commando," and the 635 the "M16A2 SMG."  At least, according to Colt's catalogs and manuals from the period.  

lol   you know what I mean smart ass

Take a Colt armorers course sometime. I've seen four position rifles marked M16A2 and full auto carbines marked the same.

...and guns marked "burst" but with full auto kits from the factory, and all sorts of other variations, but were all M16A2s.  The key "defining" feature was the 1/7 twist for the new NATO standard 5.56 round based off the SS109, but the A2 sights, A2 reinforced lowers, A2 pistol grips, A2 flash suppressor/compensator all came into play.

This is beside the point though, for the purpose of this forum, the A2 upper/rear sight should be the key defining feature (with allowances made for uppers with A1 field sights and case deflectors, as found on A2 carbines, commandos, and the Canadian derivation of the M16A2 ), with all others a secondary consideration.

Little bit of a thread resurrection, but I'd like to chime in if I can-

I think that the best way to define what "belongs" in the A2 forum would be any replica or representation of a weapon designed to fire the SS109; that is to say, the 1/7 twist barrel, or the 7xx series.  Once the 1/7 barrel was adopted, Colt more or less "re-issued" all of their 6xx series models with 1/7 barrels and created new 7xx model designations (though the M16A2 retained a 6xx designation).

On the other end of the spectrum, the cut-off would be anything using a standard "flat top" upper receiver.  At the same time, given the historical bent that a lot of members have, I would say we should definitely be able to discuss say the ACR prototypes in the A2 forum; if only because I don't have much hope for a good discussion of the ACR being possible in the normal AR forums.  It is a transitional prototype model that fits very solidly within the "era" of the 7xx series models.  

The beginning of the "era" would be the M16A1 product improvement programs that would lead to the eventual development of the USGI M16A2.  The end would be "arguably-mythical" first production run of M4 Carbines that used fixed carry handle upper receivers.  Included would be any models that were developed or introduced during this time period, as well as anything that is a replica, representation, or "spirit of" build that would seemingly fit within this period.  

By those guidelines, things like the C7 and C8, though using field sights rather than adjustable sights would be included; as would carbine variants, from the 723 to the XM4/M4 as well as other commercial, export, and non-military variants.  Things like lower profile would be irrelevant, as would whether "A2" or "A1" sights were being used, as well as barrel profile, as both the 723 with its .625 barrel and the Sporter Match HBAR 6601 would be included as well.  Essentially the way Colt defined the "M16A2 Family of Weapons" would be the primary purview of the forum.

Just my thoughts on it...

~Augee

Personally I would like this forum to just feature 20" barrelled fixed or carry handle uppers, with fixed buttstocks. They have enough carbines and SPR's in the AR discussion section.

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I consider it any rifle with a fixed A2 upper receiver.  Barrel length is not a deal breaker for me.