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Posted: 12/23/2014 10:10:20 AM EDT
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Some folks don't believe these ever existed.
Here's one I had in my armory at Quantico in 1989 or so... 
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Thank you for verifying something I've been saying for years! I've seen those pics before, didn't know they were yours. Where do you stand on Dockery's assertion that a small number of A2 carry handle M4s were delivered to SEAL teams early on? My opinion is the flattop upper came out and of course every SOF guy wanted that! Likely a lot of 727ish uppers were swapped out for A3s. If you have any additional info Sir, we'd love to hear it. I have some more books ordered, BTW - one will be headed your way fairly soon. 
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| I have an early A2 upper that has XM4 right above the gastube hole, it's a Dark Gray Colt, I've had for years, it has a light gray A2 port door and bighead FA notched to use with both A1/A2 lowers, because I believe these were originally installed on FA A1 lowers, then upgraded when the 727 came out I believe the the XM4 was the early RO720...?, I gotta confirm that, I have a writeup from Augee about this somewhere. |
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Morg,
I am not Coldblue, but I have first hand knowledge of the XM4 marked Colt carbines with M203s going to at least 1 Naval Special Warfare unit during the mid to late 1980's in Virginia Beach, VA. According to M16A2 history, the USMC developed the XM4 carbine and from what I remember, there was no money for further development or possible adoption by the USMC. A close family friend of mine was a Navy Special Agent on the Security Team of the Commandant of the US Marine Corps during the 1980s, when the US flexed its might into the Gulf of Sidra/Libya. He said he got to handle the XM4 at Quantico and he was very impressed with it around 1985. He was later assigned to the criminal investigations into the procurement of Arms, Ordnance and other special equipment by US Naval Special Operations forces, which actually resulted from a similar investigations in a compartmented security program under the US Army SOFs. He was also shown the XM4 with M203 attached at a Virginia training facility by Navy SEALs - they had the same XM4 markings. He still has a color photo of himself firing the XM4 with M203 underneath at a USMC marksmanship firing range at Dam Neck base in 1986-7. The people in the background are obviously Marine Marksmanship Instructors (campaign cover with cord) and the others were SEALs (real long hair and carrying stainless steel S&W Magnums in Bill Rogers drop leg holsters (not usually seen then). He said that the SEALs also still had modern versions of the XM177E2 Commando in both skinny 727 carbine barrel models and the 11.5 inch shorties. The SEALs had adapted a sleeve to the skinny 727 and earlier M16A1 carbine barrel to position the M203 front mount in the proper place - all of this came about from someone's recollection that US SOF had modified XM177E2s to mount the M203 back in Vietnam using the existing stove pipe flash suppressor and a modified front hand guard cap and flash suppressor spacer/insulator + M203 sheet metal bracket. The feed ramp modifications are probaby all Colt - but dont overlook the possibility that it was USMC refinement! He told me that he also saw the XM4 in full trim at the Marine Corps Show in Washington, DC at the Colt Firearms booth. He talked with the late Rob Roy, who was the Vice President of Colts Military Sales and the senior most Colt designer for the AR15/M16 system. He also said that he was escorting Gen Al Gray, who was Commandant of the USMC at the time and he heard the story confirmation about the earlier USMC development. A side note, this same Navy agent was able to get both a test sample M16A2 XM4 upper and M16A2 11.5" Commando upper from Bob Roy for testing for the Navy's VIP Protection Teams, since they still used XM177E2 marked AR15 military lowers that NSWC Crane had upgraded with 14.5 inch skinnybarrel uppers and refinished in light grey Sandstrom finish. He said after their demo and using the uppers for about a year, the Navy found the funds to purchase the M16A2 with skinny carbine barrels (727) instead of the XM4 profile - and this was in 1988. Colt was having a strike then, and he was allowed to keep both uppers, which found their way onto a privately purchased, transferable M16A2 Commando, that the Agent bought from the old AeroMarine Gun Sales shop in Alabama - just before the 1986 ban. He still has the M16A2 and 2 Commando uppers, but he said that a FNMI rep saw him shooting the XM4 upper on his privately owned weapon at the old shooting range at the Navy base at Indian Head, MD and it was quickly traded to FNMI rep for a FNC folding stock carbine, a new-engraved Belgian Browning High Power pistol and 1000 rounds of FN 9mm tracer ammo - I guess FN really wanted to see what made the XM4 special - and the Agent believed that FN used his old upper to try and get in on the M4 contracts early in the 1990s - which resulted in findings that Colt had the exclusivity on the M4 TDP (true or not, it makes a great story and the Agent still has the engraved High Power and FNC). Picture is an early one of a Seal Team 4 SEAL with a preM4 modded carbine, circa the late 1980s, with the previously used "barrel sleeve" when the XM177E2 flash suppressor was no longer available. 
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From Augee's writeup:
To clarify - there is no real "727 to XM4 to M4" evolution, Colt, being Colt, of course, made things a lot more ridiculously convoluted than that. In fact, the XM4 comes "first," and was a program that was originally spearheaded by the Marine Corps, I have heard (coldblue may be able to verify) that the "XM4" designation was not initially intended as the "next in sequence" for the M1/2/3 .30 Cal. Carbine series (CARBINE, CAL. 5.56MM, M4), but actually as a successor the M3 Grease Gun SMG family (SUBMACHINE GUN, CAL. 5.56MM, M4). This would also be consistent with the designation of the XM177 series as SMGs rather than carbines. One way or another, not long after the development of the M16A2 proper, the Marine Corps requested the development of a "shorty" variant of the M16A2. The resulting "carbine" was designated the RO720, and the other services would eventually "jump on" to the XM4 program.Initially, the intent from the Army was that the M4 would serve as a replacement for the M16A2 for armored vehicle crewmen, drivers, RTOs, etc. - soldiers who needed a defensive weapon, but would find the 20" rifle unmanageable due to the nature of their primary duties as well as airborne/air assault units. This is the reason that the M4, however it was originally intended - ended up being designated as a "carbine," though, for example, it would be "slated" to replace the Grease Gun on the MTOEs of some units. XM4 development continued throughout the 1980s, with several different barrel types being evaluated. As far as I have been able to determine - ALL XM4s should have utilized "A2 profile" lowers and S-1-3 FCGs, as they were direct developments of the military's M16A2 configuration, and all but the very earliest prototypes would have been "US GOVT PROPERTY" marked Meanwhile, Colt was not, by this time, merely catering to "official" military programs. Since the heyday of the "CAR15" family, Colt had been building a pretty extensive stable (pardon the pun) of commercial/export variants marketed to everyone from FMS to LE, etc. Anyways - the point is, that as a result - there's not really a reliable way that I have been able to determine that says that RO723s and RO727s before X serial number used A1 lower forgings, while those after serial number Y used A2 lower forgings - it was mixed in rather haphazardly, apparently simply depending on which lowers were on hand and available when the order was placed and manufactured, meaning that RO723s and RO727s with otherwise "early" features can be seen with A2 profile lowers, while others with "late" features can be seen with A1 profile lowers. Moreover, since the heavy use of the XM177 family in SEA and beyond, SOF had developed a particular fancy for shortened M16 variants. One of the more prolific variants was the Colt R653, or "M16A1 Carbine," a 14.5" barreled, 1/12 RH twist carbine that was otherwise almost identical to the XM177E2 minus the flat slip ring, barrel length, and the lack of a moderator. The R653 was heavily used by US SOF as a COTS purchase, and the specific model was even licensed to Elisco Tool in the Philippines, and designated the 653P. Essentially - Colt was almost certainly "using up" old stocks of parts that could no longer go to military contracts when they began producing the RO723 and RO727. In the case of this meant, for example, "A1" uppers without case deflectors, and for both the RO723 and RO727 - it meant that already existing forgings (likely in various stages of machining) in the "A1 profile," after the military's adoption of the M16A2 with the structural reinforcements to the lower receiver, could no longer be used to produce new military rifles. More than likely, not wanting to waste them, not thinking anyone would know or care about the difference - Colt then proceeded to use up almost all of the available "A1 profile" lowers on their commercial/export production - not just the carbines, but 20" rifles as well. |
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So... A2 Upper A2 Lower A2 Pistol Grip A2 Delta Ring M203 Cut M4 Barrel Can't tell what's being used on the back end (stock/tube/lock-nut, ect.) Looks like good times though  The M4 waffle stock wasn't issued until 2002 iirc, I'm not sure when the castle nut came about. |
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The M4 waffle stock wasn't issued until 2002 iirc, I'm not sure when the castle nut came about. Quoted:
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So... A2 Upper A2 Lower A2 Pistol Grip A2 Delta Ring M203 Cut M4 Barrel Can't tell what's being used on the back end (stock/tube/lock-nut, ect.) Looks like good times though The M4 waffle stock wasn't issued until 2002 iirc, I'm not sure when the castle nut came about. It would have a 2 or 4 position milspec buffertube/fiberlite stock body, old style castle nut and a standard lock plate. |
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One more tid-bit to chew on: M4 barrel length.
First one we tested were the shorter barrel Commando type, but they were too short to mount our bayonet. Se we asked Colt (Rob Roy) to lengthen the barrel long enough to support the bayonet. Next time we saw them they had 14.5" barrels and Colt and the Services never looked back. And the M3 SMG nomenclature to M4 is the straight scoop. We even had draft manuals made up to support our testing, but unfortunately I don't have one. |
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One more tid-bit to chew on: M4 barrel length. First one we tested were the shorter barrel Commando type, but they were too short to mount our bayonet. Se we asked Colt (Rob Roy) to lengthen the barrel long enough to support the bayonet. Next time we saw them they had 14.5" barrels and Colt and the Services never looked back. And the M3 SMG nomenclature to M4 is the straight scoop. We even had draft manuals made up to support our testing, but unfortunately I don't have one. You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. |
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You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. Quoted:
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One more tid-bit to chew on: M4 barrel length. First one we tested were the shorter barrel Commando type, but they were too short to mount our bayonet. Se we asked Colt (Rob Roy) to lengthen the barrel long enough to support the bayonet. Next time we saw them they had 14.5" barrels and Colt and the Services never looked back. And the M3 SMG nomenclature to M4 is the straight scoop. We even had draft manuals made up to support our testing, but unfortunately I don't have one. You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. This surprises me, because I think most guys here understand this to be true. IIRC, we should include A1 spec, A2 marked lowers to this possibility, since they predate the Mk18s and DMRs Crane built with refurbished A1s. Colt made a lot of "A2s" that were just A2 roll stamped A1 lowers during that time frame. I really didn't want to sell my A2 LMG upper, SOCOM barrelled upper recently, but I needed money to put into the book.  Maybe someday I'll get to keep one...I really like the weight and balance of the 11.5" Commandos best though. If I can sell enough books, it would be a dream come true to own a real 733. 
Thanks for all the great info guys. There's been a LOT of debate about the validity of this, with some well-known members like Scott Ryan saying "Those are just 727s." |
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You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. Quoted:
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One more tid-bit to chew on: M4 barrel length. First one we tested were the shorter barrel Commando type, but they were too short to mount our bayonet. Se we asked Colt (Rob Roy) to lengthen the barrel long enough to support the bayonet. Next time we saw them they had 14.5" barrels and Colt and the Services never looked back. And the M3 SMG nomenclature to M4 is the straight scoop. We even had draft manuals made up to support our testing, but unfortunately I don't have one. You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. Agree with Morg, I've always understood that to be true. Same for the XM4 being a fixed, A2 upper, and I believe it's certainly plausible some of these ended up in operational SOF units. Unfortunately, those end users rarely care about the specific/proper nomenclature like some of us do, so them calling a carbine a "CAR-15" or "M-4" without any documentation doesn't get us very far. |
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Here is a good read found on Small Arms Review. Click the FREE button to view it.
Go-Ahead In-Process Review of Carbine, 5.56mm, XM4 |
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Here is a good read found on Small Arms Review. Click the FREE button to view it. Go-Ahead In-Process Review of Carbine, 5.56mm, XM4 Very cool. The inclusion of an SP1 carbine was interesting, but what I really thought was interesting was the pencil barrel side sling adapter on the 723. Also, note all the photos are reversed negatives. |
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so, has anybody with XM4 experience, actually seen one with the barrel at the top of this pic? http://i151.photobucket.com/albums/s147/crackedcornish/dsc00733zt0.jpg It looks like the profile the Canadians used on the C8. |
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I knew Patrick A. Serao pretty well as a "young" Engineer.
We accompanied an element of the 82nd to Egypt during Bright Star 83 while I was assigned to Picatinny to access the desert environment in regard to the developing M16A2. Here we are conducting a class on the M60 Machine Gun in the desert west of Cairo: 
You might note I am wearing the Viet-Nam era Wrist Compass I discussed on another topic here...the watch is on the inside of my wrist. |
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Very cool. The inclusion of an SP1 carbine was interesting, but what I really thought was interesting was the pencil barrel side sling adapter on the 723. Also, note all the photos are reversed negatives. Quoted:
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Here is a good read found on Small Arms Review. Click the FREE button to view it. Go-Ahead In-Process Review of Carbine, 5.56mm, XM4 Very cool. The inclusion of an SP1 carbine was interesting, but what I really thought was interesting was the pencil barrel side sling adapter on the 723. Also, note all the photos are reversed negatives. Standard M203 sling mount from the 80s and 90s for use on either the M16A1 or A2 I'd assume. Based on the flat slip ring, I bet that carbine is actually a 653 that had the A2 compensator and pistol grip added. 723s would have the delta ring. The A2 uppered carbine has the middle barrel profile from the schematic crackedcornish posted. |
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Thank you for verifying something I've been saying for years! I've seen those pics before, didn't know they were yours. Where do you stand on Dockery's assertion that a small number of A2 carry handle M4s were delivered to SEAL teams early on? My opinion is the flattop upper came out and of course every SOF guy wanted that! Likely a lot of 727ish uppers were swapped out for A3s. If you have any additional info Sir, we'd love to hear it. I have some more books ordered, BTW - one will be headed your way fairly soon. Do you remember what the Colt model number for the XM4 was? RO7__? Don't know, but Colt's "Bound Books' of weapons shipped to the US Gov of that era would probably have it listed....? |
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I knew Patrick A. Serao pretty well as a "young" Engineer. We accompanied an element of the 82nd to Egypt during Bright Star 83 while I was assigned to Picatinny to access the desert environment in regard to the developing M16A2. Here we are conducting a class on the M60 Machine Gun in the desert west of Cairo: <a href="http://s1357.photobucket.com/user/D_A_Lutz/media/PatSandmeBrightStar_zpsb622f3cd.jpg.html" target="_blank">http://i1357.photobucket.com/albums/q759/D_A_Lutz/PatSandmeBrightStar_zpsb622f3cd.jpg</a> You might note I am wearing the Viet-Nam era Wrist Compass I discussed on another topic here...the watch is on the inside of my wrist.  That's what I'm talking about! Eagle, Globe, and Anchor right up front. 
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Do you remember what the Colt model number for the XM4 was? RO7__? Don't know, but Colt's "Bound Books' of weapons shipped to the US Gov of that era would probably have it listed....? Quoted:
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Thank you for verifying something I've been saying for years! I've seen those pics before, didn't know they were yours. Where do you stand on Dockery's assertion that a small number of A2 carry handle M4s were delivered to SEAL teams early on? My opinion is the flattop upper came out and of course every SOF guy wanted that! Likely a lot of 727ish uppers were swapped out for A3s. If you have any additional info Sir, we'd love to hear it. I have some more books ordered, BTW - one will be headed your way fairly soon. Do you remember what the Colt model number for the XM4 was? RO7__? Don't know, but Colt's "Bound Books' of weapons shipped to the US Gov of that era would probably have it listed....? RO727 was the production number, but I don't know that it's correct for the XM4. I thought XM series experimental weapons didn't have codes until they went into production? |
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RO727 was the production number, but I don't know that it's correct for the XM4. I thought XM series experimental weapons didn't have codes until they went into production? Quoted:
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Thank you for verifying something I've been saying for years! I've seen those pics before, didn't know they were yours. Where do you stand on Dockery's assertion that a small number of A2 carry handle M4s were delivered to SEAL teams early on? My opinion is the flattop upper came out and of course every SOF guy wanted that! Likely a lot of 727ish uppers were swapped out for A3s. If you have any additional info Sir, we'd love to hear it. I have some more books ordered, BTW - one will be headed your way fairly soon. Do you remember what the Colt model number for the XM4 was? RO7__? Don't know, but Colt's "Bound Books' of weapons shipped to the US Gov of that era would probably have it listed....? RO727 was the production number, but I don't know that it's correct for the XM4. I thought XM series experimental weapons didn't have codes until they went into production? The 727 was a parallel, but separate Colt development, for the UAE. Frank and HipShot both wrote Auggie says the XM4 was the RO720. |
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That 'Old Corps' emblem came from a stainless steel stencil I "salvaged" from a pallet of scrap metal at Camp Pendleton in 1971.
By design, it had a hole for the button of your left breast shirt pocket. Obviously designed for old Herring Bone utilities pocket stenciling of our emblem and USMC. I gave this to a fellow (younger) Marine when I retired in 1991. |
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That 'Old Corps' emblem came from a stainless steel stencil I "salvaged" from a pallet of scrap metal at Camp Pendleton in 1971. By design, it had a hole for the button of your left breast shirt pocket. Obviously designed for old Herring Bone utilities pocket stenciling of our emblem and USMC. I gave this to a fellow (younger) Marine when I retired in 1991. Very cool. |
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The 727 was a parallel, but separate Colt development, for the UAE. Frank and HipShot both wrote Auggie says the XM4 was the RO720. Quoted:
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Thank you for verifying something I've been saying for years! I've seen those pics before, didn't know they were yours. Where do you stand on Dockery's assertion that a small number of A2 carry handle M4s were delivered to SEAL teams early on? My opinion is the flattop upper came out and of course every SOF guy wanted that! Likely a lot of 727ish uppers were swapped out for A3s. If you have any additional info Sir, we'd love to hear it. I have some more books ordered, BTW - one will be headed your way fairly soon. Do you remember what the Colt model number for the XM4 was? RO7__? Don't know, but Colt's "Bound Books' of weapons shipped to the US Gov of that era would probably have it listed....? RO727 was the production number, but I don't know that it's correct for the XM4. I thought XM series experimental weapons didn't have codes until they went into production? The 727 was a parallel, but separate Colt development, for the UAE. Frank and HipShot both wrote Auggie says the XM4 was the RO720. I remember reading that thread now. Makes sense I guess. Other than rollmark, what would make a 727 different? I have to say, I really like A2/M4 carbines. They handle well, have good sights - what's not to like? |
| That's just it, you quickly get into the position where the only difference is roll marks and customers. Somewhere in there, the early 700 series carbine feed ramps were made even deeper and became the M4 feed ramps, and uppers started getting the "4" or "M4" stamped above the gas tube hole. Maybe that's "the line." I've got Colt A1/C7 and A2 uppers with feed ramp cuts, some with and some without the 4 stamp. |
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I remember reading that thread now. Makes sense I guess. Other than rollmark, what would make a 727 different? I have to say, I really like A2/M4 carbines. They handle well, have good sights - what's not to like? Quoted:
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Thank you for verifying something I've been saying for years! I've seen those pics before, didn't know they were yours. Where do you stand on Dockery's assertion that a small number of A2 carry handle M4s were delivered to SEAL teams early on? My opinion is the flattop upper came out and of course every SOF guy wanted that! Likely a lot of 727ish uppers were swapped out for A3s. If you have any additional info Sir, we'd love to hear it. I have some more books ordered, BTW - one will be headed your way fairly soon. Do you remember what the Colt model number for the XM4 was? RO7__? Don't know, but Colt's "Bound Books' of weapons shipped to the US Gov of that era would probably have it listed....? RO727 was the production number, but I don't know that it's correct for the XM4. I thought XM series experimental weapons didn't have codes until they went into production? The 727 was a parallel, but separate Colt development, for the UAE. Frank and HipShot both wrote Auggie says the XM4 was the RO720. I remember reading that thread now. Makes sense I guess. Other than rollmark, what would make a 727 different? I have to say, I really like A2/M4 carbines. They handle well, have good sights - what's not to like? I've been sitting here, debating for probably like 4 months now if i'm going to put a 20 or 14.5" bbl on this A2 upper i've had just sitting around. This thread is really starting to push me towards 14.5. I bounce back and forth all the time on the idea though. Well I guess I can order the non f marked FSB and flash hider since they're both the same. Know of anywhere to order non F marked FSB's? |
| As can be seen in the linked document from SAotW, the XM4 Carbine program was started by the US Army. In April 1983, the 9th Infantry Division initiated a Quick Reaction Program requirement document for a XM177E2 improvement/replacement program. It was one of many QRP and Required Operational Capability documents the 9ID filed that year, as they were working with the U.S. Army Development and Employment Agency and Combined Arms Combat Development Activity. As the linked document shows, the QRP was revised to dub it the XM4 Carbine as early as January 1984. The XM4 Carbine became a joint Army/Marine Corps program sometime in 1985, but the Army pulled its funding in 1986. |
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It is probably a little long term, but I am working on it. Quoted:
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Coldblue, please tell me you have a book published somewhere, preferably with pictures. It is probably a little long term, but I am working on it. It's a lot of work, I know, but I'm looking forward to seeing the finished product no matter how long it takes.
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Coldblue - I notice your friend Vince DeSiena was mentioned in the XM4 IPR document as being tasked as liaison between the Army and the Marine Corps. Thanks, I caught that too. He was a great friend and work "partner in crime" during the A2 program 1980-1983. Funny though, he didn't list himself on the attendee list. I knew most of those guys on the list because I had only recently been reassigned. Going through Pat's briefing slides reminds me of how long and expensive seemingly simple things could be. And sadly, if Fort Benning or Quantico didn't send the required funds--nothing happened. Also, no mention is made of any elements of the infamous Army hose-job on the M16A2 that links have been posted here for. Which re-affirms (to me) how little validity it had within Fort Benning, and the Army at large, since they were in attendance at this M4 meeting--and near every M16A2 improved element they could carry over to the carbine was approved.. |
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Agree with Morg, I've always understood that to be true. Same for the XM4 being a fixed, A2 upper, and I believe it's certainly plausible some of these ended up in operational SOF units. Unfortunately, those end users rarely care about the specific/proper nomenclature like some of us do, so them calling a carbine a "CAR-15" or "M-4" without any documentation doesn't get us very far. Quoted:
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One more tid-bit to chew on: M4 barrel length. First one we tested were the shorter barrel Commando type, but they were too short to mount our bayonet. Se we asked Colt (Rob Roy) to lengthen the barrel long enough to support the bayonet. Next time we saw them they had 14.5" barrels and Colt and the Services never looked back. And the M3 SMG nomenclature to M4 is the straight scoop. We even had draft manuals made up to support our testing, but unfortunately I don't have one. You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. Agree with Morg, I've always understood that to be true. Same for the XM4 being a fixed, A2 upper, and I believe it's certainly plausible some of these ended up in operational SOF units. Unfortunately, those end users rarely care about the specific/proper nomenclature like some of us do, so them calling a carbine a "CAR-15" or "M-4" without any documentation doesn't get us very far. This is true. In his book, Gen Boykin describes going into Grenada with an "M4". |
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You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. Quoted:
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One more tid-bit to chew on: M4 barrel length. First one we tested were the shorter barrel Commando type, but they were too short to mount our bayonet. Se we asked Colt (Rob Roy) to lengthen the barrel long enough to support the bayonet. Next time we saw them they had 14.5" barrels and Colt and the Services never looked back. And the M3 SMG nomenclature to M4 is the straight scoop. We even had draft manuals made up to support our testing, but unfortunately I don't have one. You know I had mention the bayonet thing to multiple people on this very forum and was told I did not know what I was talking about. Gentlemen, With all due respect, you may be referring to me, however, I think I may have been misinterpreted - I have no doubt that the above exchange coldblue says occurred occurred early in the development of what would become the M4 Carbine, and have affirmed this many times in the past - What I have said in protest to "the M4's barrel length is only 14.5" because it could mount a bayonet" is the fact that while semantically that statement may be true - the implication inherent in it is that the 14.5" barrel length and 14.5" carbine exists solely for the purpose of mounting a bayonet, which I have been unable to find any evidence of (some of you gentlemen have access to far better resources in that respect than I, however). As I've pointed out in the past - the 14.5" carbine barrel predates both the M16A1PIP/M16A2 Carbine/XM4 - and was first introduced on the R651/2 Commercial/Export M16A1 Carbine, and most famously, in the form of the R653 M16A1 Carbine. Fulfilling the request to try a longer barrel length that might accept a bayonet was not a matter of matching the barrel length to the bayonet and doing a "custom" job for that project based on a requirement, but a simple matter of going with an "off the shelf" barrel length that happened to work, and that was already being manufactured, albeit in M16A1 form. The reason that I point this out is that this anecdote is often used by "critics" of the 14.5" barrel length as a whole, not on the M4 Carbine, and used to imply that the choice of 14.5" as a barrel length in general was arbitrarily based "solely" on a Marine Corps requirement to mount a bayonet to the M4 Carbine. As for why the 14.5" barrel was chosen for the M16A1 Carbine, the most convincing argument I've heard so far (IIRC, from Chris Bartocci while he was still working at Colt) - that based on the unsatisfactory long-term performance of the XM177 moderator and the fact that it had been classified by the BATF as a sound suppressor, thereby complicating export and commercial sales, the 14.5" barrel length was developed to more or less match the OAL of the XM177E2 without using the moderator. ~Augee |
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That's just it, you quickly get into the position where the only difference is roll marks and customers. Somewhere in there, the early 700 series carbine feed ramps were made even deeper and became the M4 feed ramps, and uppers started getting the "4" or "M4" stamped above the gas tube hole. Maybe that's "the line." I've got Colt A1/C7 and A2 uppers with feed ramp cuts, some with and some without the 4 stamp. That's pretty much the practical difference. 
I suppose part of the interest is in the development pipelines, and what requests by what users resulted in what developments, and how those theoretical capabilities projections would eventually translate into operational use. There's actually a fairly "biggish" thread in the A2 subforum discussing the RO727, and along the lines, a little bit about the other 700-series M16A2 Carbines as well - As far as I know/can tell - there's never been any significant debate, at least not much credible debate that I've seen suggesting that the XM4 did not have a fixed carry handle upper. Nor would it be impossible or even unlikely that operational units would get "pre-production," "experimental" variants, e.g. combat use of the XM16E1 and XM177-series. The debate has essentially been whether or not the first production run of M4s had fixed carry handle uppers, and if so, whether those weapons would have shipped with the model number designation of "RO920," or whether they would have had a different model number, possibly "RO720." As for the question of what the XM4's model number would have been in, while I've seen a couple different ones claimed - all indications to me appear to point to "RO720" throughout the XM4's development. This would also make several more of Colt's contemporary model numbers make sense as well. Another question would then become - would SOF units really turn in their RO723s and RO727s - both with S-1-F FCGs for S-1-3 XM4s, with the M4A1 following a few months, at most, in the production pipeline? Several years back, the "accepted" belief was that the TF Ranger in Somalia ("BHD") was using XM4 uppers mounted on R653 lowers "because the Rangers wanted full-auto," now they're almost universally accepted to have been "standard" RO727 M16A2 Carbines. In terms of the M4A1, it seems very rarely disputed that the M4A1 was equipped with an accessory railed "flattop" upper receiver from the very beginning of production - it's only the M4 that appears to be in question. As for questions such as "true" M4 barrel profiles and feedramps, castle-nuts, four position receiver extensions, double-heat shield handguards, etc. - as far as I can tell - these all would have been "introduced" during XM4 development, and "debuted" with the M4/M4A1 - while the RO723/7 would have used the M16A2 commercial/export components. My belief based on my current information is that not long after the M4/M4A1 began production - the RO723/725 and RO727/729 M16A2 Carbine was also discontinued - in favor of the RO777 and RO779, which was rollmarked "M4/M16A2E." The RO777 and 779 would have been essentially the same thing as the 732/727 families, but began integrating M4 components into production, and have long been referred to as "late" RO723s or RO727s. Meanwhile, the RO777 was also accepted into U.S. military service as a COTS item - including one I got some "hands-on" (no shooting, unfortunately) time with at Bagram in 2008. As the RO777 also featured many M4 parts as well as a fixed carry handle - and used the term "M4" in the rollmark - how many people have "misremembered" COTS RO777 M4/M16A2Es for having seen "XM4s?" The RO777 situation would also help to make sense of the XM4 and M4 model numbers and commercial and export designations - when the M4/M4A1 series was type-classified and added to the U.S. military inventory, it also had an effect on Colt's commercial/export line. Assuming that the XM4 retained the model designation of "RO720" - M16A2 Carbine - RO723 - S-1-F - A2/FS Upper RO725 - S-1-3 - A2/FS Upper RO727 - S-1-F - A2 Upper RO729 - S-1-3 - A2 Upper XM4 Carbine - RO720(?) - S-1-3 - A2 Upper RO721(?) - S-1-F - A2 Upper(?) USGI M4 Carbine - RO920 - S-1-3 - A2 Upper(?)/Flattop Upper USGI M4A1 Carbine - RO921 - S-1-F - Flattop Upper M4/M16A2E - RO777 - S-1-F - A2/FS or A2 Upper RO779 - S-1-3 - A2/FS or A2 Upper Commercial/Export M4 Carbine - RO977 - S-1-F - Flattop Upper RO979 - S-1-3 - Flattop Upper These M16A2 to M4 component changes would also have been adopted "in stride" to the R6520 AR-15A2 "GOV'T CARBINE" - This would also explain the "large" number of "4" or "M4" marked A2 uppers available second-hand - they could/would have been used not only on XM4s, but RO777/9s as well as R/LE/AR6520s, and all the ban-era variants until relatively recently. ~Augee |
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One other part of the M4 story is the origin of the Ramp Angle changes to the eventual M4's barrel extension. This naturally led to the M4's upper receiver having corresponding cuts for improved feeding, and thus the "M4" marking at the front of the upper. The ramp angle change came about in early USMC sponsored extreme cold weather testing at Aberdeen Proving Ground. Colt's response was the ramp angle change and the retested weapons passed.
I also remember a meeting we had with Lorn Brunton (of the A2 case deflector fame) concerning integrating the then new "M4 ramp angle change" (RAC) change into the technical data package for the M16A2 rifle, but he would hear nothing of it because it would "mix" upper receivers into the fleet and cause two different A2 barrels and uppers to be stocked in the Supply System. In the back of my mind however, I was ready to roll with his opinion and when I finally agreed, he then accepted the RAC even though an hour earlier he was dead set against it.--all for the sake of parts "interoperability." |
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Some folks don't believe these ever existed. Here's one I had in my armory at Quantico in 1989 or so... <a href="http://s1357.photobucket.com/user/D_A_Lutz/media/XM4USMC_zpsdfe5c9ff.jpg.html" target="_blank">http://i1357.photobucket.com/albums/q759/D_A_Lutz/XM4USMC_zpsdfe5c9ff.jpg</a> Silly question, in the top picture does the handguard cap have cuts or is it round?. I built two, one with and one without the cuts. |
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Not being able to recall any Colt model numbers and also the fact that we used GAU-5 as terminology for the carbine, when I was in USAF/EOD circa '91 to '94 we had 10 M4 fixed carry handle 14.5 inch carbines with standard M4 barrels, fiberlite stocks, I do not remember if they were 2 or 4 position, they were however safe, semi, auto and if I had had the presence of mind to take pictures back then i could prove that the US Military had Bushmaster M4s, I do recall the snake and purple tint on some of the lowers.
I have also seen Rangers with fixed carry handle M4s as well, maybe I missed something reading this thread but it seems that the use of A2 carry handle M4s was in question? Oh and by the way, we had at least 1 full 12 weapon hardigg case full of mint 601s as well, I had to count and insepct all of these, including the M4s many times per year as supply was my secondary duty, if had only thought back then, "pictures of all these would be great to have some day" but alas I was young and worried more about other pursuits... |
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