Upper receivers, bolt carriers, bolts, firing pins, firing pin retainers, ejection port doors, rear sights etc.
Album by willyp. Photos by willyp. 1 - 29 of 29 Total. 13103 Visits.
Primer on M16 upper variants There are a large number of differences in forging styles & machining in m16 uppers, this pic shows the location of the differences, the upper in the pic is a 602, 1962-63 era & has all the very early features. A: straight vertical line in front of port door. B: area under rear of port door is "indented" under the door. C: base at rear of carry handle is cut in angles, not rounded as later D & E: Both vertical lines are straight. F: pivot lug is counterbored on left side. All these areas incurred "modifications" as time went on, more pics of these areas will follow & will be referred to by the letters here, A, B, F etc.
Area A Area A, front of port door Top: early straight vertical line Bottom: later curved vertical line This area was straight from 1959 to approximately 1966 then transitioned to the rounded type. The rounded area on the upper shown is very pronounced & is not always this "rounded", some uppers have a rounded profile in this area that is actually difficult to ascertain w/o having an earlier straight profile upper next to it!
Area B under port door B, under rear of port door Top: line indented to right, early Bottom: Line not indented, later This area was indented up to approximately 1965 then went to the unindented profile afterwards. The indented style here will always be found w/the straight contours at A, D & E.
Area C, angled Area C, base of carry handle where charging handle locks into upper. On the 601 & early 602 this area was angled (into early 1963?) the charging handle shape was changed from triangular to the now rounded style, this area was rounded in profile after early 1963 thru to today.
Areas D & E D & E, on left side of upper, the vertical lines near bottom. Top: straight vertical lines, early Bottom: curved near top vertical lines, later This is a very difficult area to identify on these uppers, most very early uppers (601, 602, very early 603 & 604 uppers w/indent at B) are very straight, sometimes w/a very slight mild curve, "mid early" (1965-1966?) do not have the indent at B, are usually very straight at A, D & E though sometimes have a slightly rounded profile, other times striaght! "late" 603/604 uppers have no indent at B, obvious round profile at A, & slightly rounded at D & E! Interestingly on some of the following "modified A1 or C7" uppers with the cartridge deflector the areas at D & E are straight like the very early & mid 603/604 uppers!
601 upper First military production M16 type upper, all very early forging features, "slickside" upper meaning no forward assist housing, these uppers had no sight markings on right side by the sight wheel, all later uppers (up to the A2) had sight markings on the upper itself, the 601 had the rear sight markings on the sight wheel itself. The 601 also had a small hole drilled under the opening of the ejection port door, the "tail" of the port door spring sat in this hole.
601 port door spring hole Here you can see the straight forge profile in front of the ejection port (became rounded after about 1965-6) per Ekies exc article on ar15.com!, also the markings, C & VP in a square at the base of the handle in front & the small hole in the receiver under the ejection port for the port door spring, this was found on the 601 & early 602's only.
602 upper Early 602 upper, the early 602 was the same as the 601, the exception being the markings for the rear sight are now on the upper itself, on the 602 these markings are inset/engraved on the upper, on all later models they were raised. Later 602 uppers did away w/the hole for the ejection port door spring & had the rounded profile in area C as they used the "improved" later type charging handle.
Civilian Colt SP1 upper The SP1 uppers used a larger diameter front pivot pin hole & double head screw as a pivot pin, they are not directly interchangeable w/small pin lowers w/o the use of an adaptor. The SP1 went into production in 1964, the early SP1 uppers had same forge profiles as the 601/602 uppers, later models went to the rounded later style, all SP1 uppers used the raised style sight markings on the upper which began w/the 603/604 series. None of the early SP1 uppers I've seen or heard of have the hole for the ejection port door spring.
604 upper This style upper was used on AirForce rifles (model 604), it's a "slickside" as the AirForce did not want the forward assist on their rifles, these went into production late 1963, very early examples used the early straight contours in areas A, D & E & the indent in area B, all used the later round profile in area C & the raised sight markings on the upper. Very early style was approximately 1963 thru 65, the indent in area B was omitted approximately 64/65 & the rounded profiles in areas A, D & E began to appear in 66-67. A lot of dealers & colllectors refer to these as A1 uppers, they are NOT A1 uppers, they are 604 uppers, they were also used on AirForce contract carbines, an A1 upper has a housing for a forward assist (FA).
Modified 603 upper Commonly known as a 605 upper in collector/builders circles due to a number of them being on 605 carbines these uppers are actually "modified 603" uppers, very early in mfg of the 604 Colt had a problem w/the supply of 604 uppers, to maintain production of the AF 604's they modified some uppers for Army 603's w/the FA housing by machining off the housing, very few were done & production picked up quickly. These modified 603 uppers were most probably used on some 605's as the 605's were built on a very small scale & almost on a per gun basis, not all 605's used these uppers but they've become the most popular for a 605 replica. All the uppers in this style I've seen are very early pattern, straight contours at A, D & E, indent at B & round at C w/raised rear sight markings.
603 (XM16E1/M16A1) upper The 603 upper (for the Army) had the forward assist added, other than that they are identical to the AirForce 604 uppers & follow the same progression in contour features & dates as the 604. Shown here is a very early 603 (A1) w/all straight contours & indent in area B. These uppers were used from late 1963 on the XM16E1 thru the M16A1 in the late 70's. The XM16E1 was the designation given by the Army to the 603 in 1963 while it was still not considered a "standard" military arm, once it was officially adopted as standard in 1967 the designation was changed to M16A1, the M16 designation was assigned to the Air Forces model 604 without the forward assist.
Later type "modified" M16A1 upper Next upper version was this type which added a cartridge deflector on the right side behind the port door which protected left handed shooters from ejected cases. These came into being in the late 70's & show all later contour features. It's unknown (& doubtful) if any of this type were used in original M16A1 production but appear to have been used as military replacement parts during overhauls. This style upper was also the type originally adopted by the Canadian military in the 80's for their C7 rifle & are usually called "C7" uppers. They were used on some later carbine variants (723 & early 727) variants that were purchased on a small scale by the US military in the mid-late 80's.
M231 "firing port weapon" upper The M231 "firing port weapon" was an M16 variant designed to be used in the M2 Bradley Infantry Fighting vehicle, they were select fire only, were stored in the M2 & "plugged" into the firing ports of the M2 using a large threaded collar. M231 uppers can be identified by the rear sight of the upper, they didn't have one! There was no sights on the M231, in the pic above you can see there is no hole/threading foe the rear sight in the upper although the raised markings are there. They also did not have a forward assist. An interesting point on this upper is that it is a later production upper, has the forge code CM but has the very early feature in area B, it's indented under the rear of the port door. I do not know if this is coomon to all m231 uppers as I've not seen enough of them to speculate. Web pic, not mine.
M16A2 upper. At the request of the USMC Colt developed the A2 which had a fully adjustable rear sight as opposed to the A1's windage only rear sight. These uppers are sued on the M16A2 & some early carbines (723, 733, 727 & 733). Some of the uppers used on the carbine variants will have "ramps" milled into the face under the barrel extension to assist in feeding the cartridge fromt the mag. These uppers all have the rear sight marking of 8/3 for both the rifle & carbine.
M4 "flattop upper" The next (& current) upper is the flat top upper which has an integral weaver rail & can be fitted w/a removeable carry handle (shown here). These uppers are used on the M16A4 rifle, the M4 carbine variant of this upper has large ramps milled into the front of the lower under the chamber/barrel extension to assist in feeding, M4 carbine uppers w/the ramps will be marked 4 or M4 on the flat by the gas tube hole on the face of the receiver, rifle uppers do not have these ramps & are not marked by the gas tube hole. The rear sights on the removeable carry handles on both models will be marked 6/3 & use a FSB that is slightly taller (from the barrel to the shelf for the sight post) due to the deck height of the upper being slighty taller which raises the position of the rear sight, these uppers, whether on an M4 carbine or an A4 rifle will use the FSB that has the F marking on the left side, this indicates the taller shelf height for the front sight post. It should be noted that the Canadi...
601, 602, 603/4 rear sight comparison Left: 601 type, no markings on upper, arrow & R on sight wheel, this style sight wheel is specific to the 601. Center: 602 type, arrow & R engraved into upper, sight wheel marked w/numbers, this sight wheel used on all uppers until the A2. Bottom: 603/604 type, raised arrow & R on upper, numbered sight wheel. All rear sights were adjustable only for windage until the adoption of the M16A2.
M231 upper rear sight In addition to the previous rear sight variants there is also this variant which is specific to the M231 "port firing weapon" for the M2 Bradley Fighting vehicle. Note there is no hole for the rear sight screw/attachment as the M231 had no sights. Pic is a web pic & not mine.
A2 A4 style rear sight comparison Top: A2 style, fully adjustable, windage & range, "base" setting marked 8/3 on range wheel. This sight on all fixed handle uppers, rifles & carbines. Bottom: A4/M4 style, fully adjustable, base setting marked 6/3 on range wheel, used w/all flat top models, M16A4 rifle & M4 carbine series in conjuction w/taller F marked FSB.
A1 type triangular forward assist (FA) button In late 1963 at the request of the Army who required a manual bolt close feature on their version of the M16 (the model 603) this is the 1st type of FA button (typeI), triangular in shape & is the type seen on any M16 model w/forward assist during the VietNam war, it was superceded very late by the typeII large round FA in the mid-late 70's.
Late A1 Large round forward assist This is the 2nd style forward assist (typeII), it's a large diameter full round (has 5 "rings"), these seem to be found on very late A1's or guns that had gone thru an arsenal refurb & may be replacement parts, they can also be found on some civilian guns after the SP1 models. This pic shows the button on a replica rifle built as a very late or refurbed A1 w/an A1 upper that has the cartridge deflector.
Early A2 forward assist button The early A2 forward assist had a large diameter round head (typeIII) that had a flat milled into it to clear the "beefier" strengthened rear reciever extension on the A2, seems to be found intermitently on A2's mid 80's.
"Standard" later small forward assist By the late 80's this small diameter (3 rings) forward assist button (typeIV) was standardized & is in use till this day, found on most A2's, all A3's, A4's, M4's.
C ejection port doors
603 (XM16E1) Bolt group right This is a 603 (XM16E1) bolt/carrier group. it's chromed but has the milled serrations on the left side for the forward assist which the Army required on their rifles, the Air Force didn't want the forward assist, after the mid 70's all carriers were mfg w/FA serrations to simplify logisitcs & the AF used these bolts in their rifles w/o the forward assists.
603 (XM16E1) bolt group left Here you can see the early style firing pin retainer, the small chrome circle about mid way just under the rear of the carrier key, this was later changed to a much simpler retainer that resembles a small cotter pin.
604 bolt/carrier group right
604 bolt/carrier detail front top Early M16/AR15's came w/chrome bolt carriers & bolts, 601, 602 & early 604's were smooth on both sides as there was no forward assist. Early carrier keys were round in profile, later ones (shown here) had a square profile just up to the gas tube port. it's believed 601 & early 602's had the round keys, late 602's & 604's had the square keys.
