I'm considering building an M16A2E4 clone, (AR15A2E4). Would you consider an A2E4 as an A2 or an A4 in all reality? I'm in the middle of a build and have been debating on weather or not to go full blown A4 or go with a A2E4 clone. From what I can tell the only difference between a standard A2 and an A2E4 is the A2E4 has a flat top receiver, where as the A4 is a flat top and Knight's M5 RAS, instead of the standard hand guard. I kind of like the look of the of the A2E4.
A2E4? Never heard of it. The A4 is the flat top A2 as far as I know. The RAS does not change the designation of the A4.
You're missing it.
The M16A2E4 isn't a retrofit of anything - it's an "enhanced" M16A2, the fourth pre-production enhancement - in this case, a flattop upper receiver.
The "E" series designation in U.S. Army (all the other services get most of their small arms through the Army, though exceptions exist, Navy designations tend to use "MK" designations, while the Air Force sometimes uses a "GAU" designation) small arms nomenclature designates an "Enhancement" to a design that has not yet been accepted as a full production variant and given an "Alteration" ("A") number.
Not all "E" designations result in a fully "type classified" designation, but some do. In order to really understand this, you ought to know that a "X" prefix also represents and "eXpirimental" design.
When applied to the M16 FOW (family of weapons) it goes a little bit like this:
The Colt Model 04 (R604) is accepted for evaluation and field testing as the XM16. Persuant to Army requests, a forward assist assembly is added to the Army variant, and designated by Colt as the Model 03 (R603). It is fielded as the XM16E
Once the trial of the preproduction XM16 and XM16E1 are finalized and completed, production variants have the "X" experimental designation dropped. Furthermore, with the XM16E1, the "Enhancement" designation is accepted as an "Alteration" [to the M16] and given the designation M16A
Years later, when a "new" M16A1 variant is being developed, the Colt R645 is tested and designated as M16A1E1 - no "X" designation is necessary, since the M16 FOW is already a production model, however, this represents an enhancement ("E") to the M16A1. So, the rifle becomes designated as the M16 - Alteration 1 - Enhancement 1. The M16A1E1 is eventually designated M16A2 when it becomes a full production model.
The M16A2 goes through a couple of "enhancements" throughout its lifetime - many of them related to the defunct ACR program. M16A2E1 and M16A2E2 are developed and tested as preproduction samples, but never put into production.
Meanwhile, the Navy SeaBees request a variant of the M16A2 that fires S-1-F instead of S-1-3. Preproduction variants are built - and issued to line units designated M16A2E3. The M16A2E3, the M16 - Alteration 2 - Enhancement 3, is eventually confirmed and type classified and put into production and becomes designated the M16A3.
Close to the same time, the flattop idea, which has been being explored almost since the XM16 (the model 656, as well as the ACR variants have used variations on the flattop idea for scope mounting - plus in the civilian sector, many "knowledgeable" shooters are having their carry handles milled off, and Weaver rail bases attached to their receivers) matures into a viable production change. Because optics are becoming more popular, the military becomes more interested in this option, and the M16A2 is given its fourth enhancement, a flattop receiver. This rifle is designated the M16A2E4, M16 - Alteration 2 - Enhancement 4. Colt jumps the gun on this and names some of its civilian variants using flattop receivers "AR15A3s" in anticipation that the military will eventually adopt the M16A2E4 and designate it the "M16A3." The repurcussions of this hasty naming are still felt to this day - flattop upper receivers are still referred to as "A3" receivers by people ignorant of the history of the M16 FOW. An "A3" receiver is in fact nothing more than an A2 receiver. The difference between the M16A2 and M16A3 lie solely in the fire control group. Likely Colt thought it unlikely that the military would sanction an entirely new "Alteration" designation for such a simple modification, but they did.
Therefore, when the flattop variant of the M16A2, the M16A2E4 went into production, its designation changed from M16A2E4 to a full blown "Alteration," next in series after the M16A3 - thus, the M16A4.
Around this same time, the whole XM4, M4, M4A1 saga is going on as well. As a sidenote, the M4 is designated not as a rifle, like the M16, but as a carbine, and the numbering convention follows in sequence from the M1 Carbine, M2 Carbine (an FA M1), and M3 Carbine (an M2 with an IR sight). Further complicating this is that the M4 Carbine is issued as a replacement for, among other things, the M3 Grease Gun, which is however classified as an SMG. On the other hand, the XM177-series is an experimental SMG, not carbine.
Furthermore, as demonstrated with their jumping the gun on the "A3" designation, Colt tends to use "military sounding" designations for their commercial models - for example, late M16A2 carbines (commercial variants) like the RO723 and RO727 are, for a short time released with lowers marked "M16A2E/M4" which looks like it's following some sort of military Alteration and Enhancement designation, but is not sanctioned, and simply a commercial designation.
Anyways, returning to the M16A4 - the M16A4 is just an M16A2 with a flattop upper receiver. Nothing more spectacular, the M16A2E4 designation ceases to exist once Alteration 4 becomes type classified. The vast majority of M16A4s are originally issued with standard A2 handguards and detachable carry handles. Remember, rail systems and optics do not become "standard" for conventional forces until well into GWOT - post-2004.
At the same time, SOCOM is issuing the KAC M4 RIS (Rail Interface System) with its M4A1s - these are "SOPMOD M4s." On the other hand, the "big Army" considers the RIS mounting system to be insufficient, and requests a redesign of the mounting interface that results in the M4 RAS (Rail Adapter System). A version is supsequently developed for the 20" rifle as well, as the M5 RAS. Note that no M5 RIS exists. Of course, the Army, in its infinite wisdom, designates the RAS as the "ARS" - Adapter Rail System - so the KAC M4 RAS is designated by the Army as the M4 ARS, while the M5 is the M16 ARS. Confused yet? We're not done.
Because at this time, the mounting of the ARS is not an "across the board" standard, M4s and M16s with the ARS installed are designated with the suffix MWS - "Modular Weapon System." SOCOM, on the other hand, while they had been initially satisfied with the RIS sees no reason not to upgrade to the better, new RAS - and begins to issue the M4 RAS in place of the RIS. For a short while, the M4A1 SOPMOD and M4 MWS are almost visually identical. Of course, one would think that the RIS would then go out of production at this time since SOCOM has upgraded to the RAS - however, the Crane MK18 Mod 0 CQBR - not a SOCOM weapon, still specifies the use of the M4 RIS, meaning that KAC maintains contracts for the RIS and continues producing them long after they're obsolete - the MK18 Mod 0 only recently having had its spec updated to use the RAS, and the RIS finally discontinued.
On the conventional side - issue of the ARS becomes more and more common, until basically all M4s and M16A4s have the ARS installed and are technically considered MWS. Of course, saying and writing "MWS" all the time becomes tedious and annoying, so many people simply drop the "MWS" suffix when referring to the weapon systems, until a vast majority of end users have no idea that the proper nomenclature for their ARS equipped rifles should include the "MWS" suffix. This has become so common - and the "standard" the MWS, that many official documents have dropped the suffix, as the use of the ARS becomes almost a given, though non-MWS weapons still exist in pockets in the inventories.
Why the MWS doesn't really receive an "E" or even an "A" designation is hard to say, except that many non-program enhancements were fielded during GWOT faster than the bureacracy and nomenclature could catch up - items becoming standard attachments before they could even be given names. Things like the TA31F ACOG which has been in use almost since Day 1 with conventional forces doesn't get a designation until the development of the TA31RCO-A4/M4 in 2006 as the AN/PVQ-31A and B. Neverminding that SOCOM, who has been using the TA01NSN as the 4X DOS has since upgraded to the TA01ECOS which is designated (AN)SU-237/PVS. Furthermore, the Army requests their own version of the AN/PVQ-31B resulting in the adoption of the M150RCO. Trijicon is not the only example of this backwards-ass nomenclature - but perhaps one of the most extreme - just to recap, the official designations of 4x32 ACOGs in service include:
4X DOS (Day Optical Sight) - TA01NSN
TA31F (RFI - COTS) - (same as) the RFI designation refers to the Rapid Fielding Initiative, in which units were issued COTS items that had no real designations yet
AN/PVQ-31A - TA31RCO-A4
AN/PVQ-31B - TA31RCO-M4
M150 RCO - M150RCO-CP
SU-237/PVS - TA01ECOS
Meaning one commercial series of sights has received a SOCOM description, a COTS description, a PVQ designation, an M designation and an SU designation.
Compared to that, the nomenclature conventions of the M16 FOW are positively transparent!
In the meantime, the Colt model designation for the M16A2E4 / M16A4 has never changed - it's the RO945. The 945, however, is the U.S. military only model - just as the RO920 and 921(HB) are government models.
Yet, Colt, having provided so many M4s with the ARS installed as OEM has designated that the RO925.
Commerical / Export variants, however, despite being identical in features, are given separate designations - RO977 is the Commercial / Export M4 Carbine (even though it's more similar to the M4A1 - S-1-F), while the RO901 is the M16A4. Many times, it seems like even Colt can't seem to keep its own model numbers straight, as throughout the history of tyhe M16 FOW, model numbers have been skipped, re-used, mis-identified, changed mid-production, and confused by different departments of the company. Not to mention model numbers usually follow complete weapons - making it difficult to determine the identity of parts - for example a 14.5" M4 gov't profile upper assembly could be an SP6921, RO920, RO921, RO925, or RO977 assembly.
Anyways... sorry for the long-winded answer - I actually saw this thread last night, but was too tired to respond at the time. It doesn't look like it's been clarified much in the interim.
Basically - the M16A2E4 no longer exists. It's the pre-production version of the M16A4. Nevertheless, it is a factory configuration, not a retro-fit. Retro-fits that are brought up to M16A4 specifications become M16A4s, just like all the M16A2s that exist that are built on A1 or earlier lower receivers.
The M16A4 with the ARS (KAC M5 RAS) is technically considered an M16A4 MWS - however few use the "MWS" suffix anymore, and simply refer to it as an M16A4.
Hope this helps,
Thank for the clarification. So I guess this project will actually be an M16A4 clone. I have an A2 upper around here some where which I plan on using in my next build. Again thanks for the clarification. You learn something new every day.