Over the past few months I have been building up a few retro style AR15s and even a couple of more modern style rifles. In all cases though, the weapons have been military style and as close to milspec as i could make them. During my research to determine which parts to use (and more often than not, which not to use) I went through a lot of data. I wish I could read and enjoy the photographs in any of the great books out there on the AR, but we must use what we have to hand right? I thought I would share what I have learned about the AR, with special focus on the development and early models. I will point out right now that some of the Colt model numbers are contradictory and i did my best to reason them out. This seems especially true with the M16A2 and M4 carbines. Hey, this is a free read and just something I am doing for fun.
Update: If some of this looks familiar, its because I posted it a year
or so ago. I was assembling an M16A1 for a goon and also updating 2 of
my own builds, so I thought i'd also update this thread and repost it
for those without archives. I have added new pictures, a timeline of
early changes, and corrected some information.
Where to start with what would become the M16 and arguably one of the
most recognizable military firearms in the world? WWII changed warfare
in many ways. Automatic weapons were seen in more hands than ever
before, fighting was highly mobile, at closer ranges, and towards the
end of the war the world's first assault rifle appeared: the German
STG.44 (MP44). After the war, the race was on to develop new kinds of
military small arms and new doctrines to utilize them. In 1948, research
at John Hopkins University indicated that as much as 95% of fighting on
the modern battlefield occurred at ranges under 300 meters. Further
research showed that soldiers who took time to aim really didn't
increase the overall kill ratio. In fact, some evidence even seemed to
suggest that 2 out of 3 soldiers in a battle might not have even fired
their weapon. It was concluded that soldiers were more likely to fire
their rifle if it had automatic capability and thus more bullets
equalled a more effective fighting force. Of course i am paraphrasing
big time here to get accross the point that by the late 1940s, it was
becoming clear that individual soldiers would be more effective if
equipped with assault rifles, instead of more accurate bolt actions. In
1953, Project SALVO began with the goal of evaluating new possible
military small arms and calibers.
At the same time, the Armolite company was founded. Armolite was not to
be a fullscale manufacturer of firearms, but rather an idea company. It
was owned by Fairchild Engineering, an aircraft firm. So Armolite
brought airplane materials and technologies to the firearms industry.
Armolite was meant to create new designs, test them, develop them, and
then sell them to other firearms companies. In 1953, inventer Melvin M.
Johnson was hired by Armolite to be a consultant. Johnson was the
designer of the M1941 Johnson rifle and light machinegun. He brought his
rotating bolt with 7 lugs system with him to Armolite, which is how it
wound up in the AR-10 and thus the AR-15. In 1954, Eugene Stoner joined
the team which was developing the AR-10. It is incorrect to say that
Stoner actually created the rifle; though he did introduce the direct
gas impingement system to it. Again though, Stoner was not the first to
use DI in an automatic rifle. That honour actually goes to the French in
1901 with their Ent B5 prototype. The system had previously been
successful in the Swedish AG-42 Ljungman and French MAS-49. It was
popular for its simple design with fewer parts, lighter weight when
compared to pistin systems, and for the fact it allowed for better
accuracy when compared to other methods. Stoner had more to do with the
materials the AR-10 was built from and its rather unique layout. The
original rifle used a steel barrel, titanium muzzle brake, and fiber
glass furniture. Though variations definitely existed.
Starting in 1954, the US military began testing to select a new service
rifle for its troops. The AR-10 was a late comer to the trials in 1956
but did make it in. It competed against the T-44 (Springfield M14) and
H&R T48 (licensed copy of the FN FAL). The AR began with a
disadvantage and was quickly dismissed from the trials when in 1957, a
test rifle's barrel burst; nearly taking off the shooter's hand and
definitely scaring the shit out of him. George Sullivan, the President
of Armolite, was basically to blame for the failure of the rifle. While
Stoner wanted to use a traditional steel barrel, Sullivan insisted on
developing an aluminium barrel and another aluminium one with a steel
liner. It was one of these barrels that malfunctioned at the trials.
That was basically the end of the AR-10 as far as the US military was
concerned. It was probably inevidible that the Springfield M-14 was
going to win anyway. The AR-10 did find limited success overseas, but
what makes it important today is how much influence its design had on
the later AR-15.
the Armolite AR-15
Even as the new 7.62x51mm NATO cartridge, along with the M14 was being
adopted in 1958, many in the military were wanting a small caliber
bullet. This lead to the Small Calibre High Velocity Program. It was
suggested to Stoner and Armolite that they should scale down the AR-10
and work on a .22 caliber projectile for it. Both Remington
andWinchester began work on similar cartridges. The military
requirements for the new rifles were that it had to weigh less than 6
lbs fully loaded, had to be capable of selective fire, had to chamber a
.22 caliber rifle cartridge, and that it had to be capable of
penatrating a steel helmet at 500 meters. By 1958, the new AR15 was
ready for testing. During a test in March of that year, another barrel
burst, but this time it was blamed on rain water and steps were quickly
taken to prevent this from happening again. The rifle was also tested in
Alaska in the Arctic climate. Complaints were quick to appear and
Stoner was sent for. He was supposed to bring replacement parts and
service the prototype rifles. When he arrived he found the rifles in
horrible condition, mistreated, assembled improperly, and not properly
cared for. It was clear the AR15 was setup to fail and indeed it had
been rejected even before he had arrived. Not all reports about the AR
were negative though. In a mach-up battle situation, it performed well
against the M-14 and Soviet AK47. It also helped that in the new trials,
it had no real serious competition.
Nevertheless, by 1959, Fairchild had become impatient with Armolite's
lack of financial success with the AR-10, AR-15, and the .223 Remington
cartridge. In December of that year, Colt officially purchased and took
over manufacturing of the line. Colt AR15 production commenced
immediately and Colt wasted no time in marketing the new rifle. Malaysia
was the first nation to purchase a major contract and the British SAS
also expressed a strong interest. In otherwords, Colt realised the main
problem with the rifle wasn't the design itself, but the way it had been
marketed and promoted. Quite honestly, Colt simply knew how to make it
happen. It wasn't just that though, Colt engineers also introduced a
number of changes to the design and in 1960, Stoner left armolite and
joined the rifle's new manufacturer.
the Early Colt M16 (601 & 602)
Probably the biggest change from the Armolite AR15 to the early colt 601
was the charging handle. The Armolite rifle had a trigger style handle
located inside the carry handle. Though this design might seem
interesting and unique, it prooved problematic. So Colt relocated the
handle to the now familiar place, though the handle was of an early
triangular shape, unlike the modern one we know today. Colt added and
standardized a 3 prong flash hider to the design. The Armolite AR often
did not have any flash hider. Next Colt standardized the furniture style
and mounting. Very early rifles had plain brown furniture, which soon
after began to be painted green. Several small parts were slightly
upgraded and changed too. Colt's first production AR was labelled the
601 or Model 01. This was the first version to actually go into combat.
In July of 1960, General Curtis LeMay whitnessed a test of the rifle and
was intrigued. A year later, as commander of the Airforce, LeMay
ordered 80,000 601s to replace the Air Force's stocks of aging M1
Carbines. However, General Maxwell D. Taylor convinced President Kennedy
and others to not allow the purchase order to go through. His reason
was that the military should not have two different rifle calibers in
service at the same time. Though Kennedy went along with Taylor's
recommendation, it seems he rather liked the AR15. Colt gifted 2 of the
rifles to the President and reports indicate he was quite taken with
Project Agile was the Colt AR-15/601's famous military debut. In October
of 1961, William Godel of ARPA sent 10 of the rifles to Vietnam for
evaluation and testing by the South Vietnamese Army and their US
advisors. Initial reports were favorable and 1,000 more rifles were sent
over the following year. I won't get into the whole wounding and
tumbling stuff that the AGile reports claimed the AR-15 capable of with
its .223 caliber and 1 in 14 twist rifled barrel; I will just say the
soldiers who used the rifle in these early trials were impressed by its
performance. The Agile reports undoubtedly contributed to the military's
continuing interest in the platform, despite political resistance. By
the end of 1962, the Air Force had already adopted the Colt 602 as the
M16. The major change from the 601 to the 602 was in the rifling. The
602 featured a 1 in 12 twist rifling pattern, which was felt to perform
better in colder climates.
In January of 1963, the U.S. Secretary of Defense Robert McNamara
ordered a hault to M-14 production. By that time, it was becoming clear
the M14 was too costly and time consuming to produce to equip the
military for the numbers of rifles it required. The AR-15 could be made
faster and more cheaply than the M14 and it was to become the new
service rifle for all the branches of the United States military. The
Army adopted an experimental version of the AR as the XM16E1 and ordered
85,000 weapons. The XM16E1 was basically the same as the early M16, but
with the addition of a forward assist. It must be noted and is
frequently pointed out, that this addition went against the advise of
both Colt and Stoner. Other changes from 602 to the 603 (XM16E1)
included: cast front sight base changed to forged, drain holes added to
the front sight base and buttstock screw, improvements to the firing
pin, upgrade to the current style of charging handle, and a new style of
pivit pin. It should be noted that some of these changes were not
implimented until 1966 or there abouts. The Air Force already had some
M16s in inventory, but was allowed to acquire 19,000 more at the same
time. The USAF rifle would not feature the forward assist, but other
upgrades made to the design throughout the decade would be incorperated
into its M16 design. The M16 was the United State's first major
fullscale adoption small arm to be sent directly into combat; without
prior extensive testing and/or peacetime issue. This fact would quickly
make itself felt.
The M16A1 (603 XM16E1 & M16A1)
The first M16s to reach Vietnam were issued to special forces, but by
1965, the XM16E1 was in theatre in ever increasing numbers. At the same
time, the Secretary of Defense approved the rifle for issue in all five
branches of the military. It wasn't long though before field reports
started to come back that painted the new rifle as a jamming piece of
junk. Many even said it caused soldiers (Marines mostly) to loose their
lives. The number one problem seemed to be a failure to extract
malfunction, in which the spent casing became stuck in the chamber.
Almost everyone in the firearms community today knows the root cause of
this problem. Stoner had originally used Improved Military Rifle (IMR)
powder in the .223 cartridge, or more simply 'stick powder.' The
military changed this powder to the common ball type to both save on
costs/use existing stocks and to give the caliber a bit more range. Ball
powder burned faster. This combined with the original lightweight
Edgewater recoil buffer/spring guide caused the rifle to cycle faster,
which in turn left more residue in the bore after firing. So the weapons
were being subjected to more parts wear than was originally allowed
for and were running dirtier than they were capable of handling, at
least reliably. Compounding the problem, Colt marketed the M16 as a
'self cleaning' firearm and did not distribute it with a cleaning kit. A
Congressional investigation ensued as soon as word of the malfunctions
and attributed loss of life, reached North america. Colt set about
fixing the problem. First, cleaning kits were immediately issued with
the weapon, along with cleaning guides. Next, the XM16E1 received a
chrome plated chamber to aid in extraction. Finally, the ultra-light
Edgewater buffer was replaced with what we know today as the standard
rifle buffer with internal weights. These improvements greatly increased
the rifle's reliability. Despite its problems, the M16 was there to
stay and in 1965, the Army ordered 100,000 more units. The same number
was ordered the following year.
In February of 1967, the XM16E1 was standardized as the M16A1. In
addition to the chrome lined chamber, the A1 differed from the E1 in
several ways: the 3 prong flash hider was replaced withA1 style 6 slot
'birdcage' type in late production e1s and standardized with A1, solid
body buttstock replaced with hollow one with a compartment for the
cleaning kit, rear sling swivel became fixed instead of rotating, a 'mag
fince' was added around the magazine release to prevent it accidently
being hit, a drain hole was added to the buttstock screw, and the
original Edgewater buffer was replaced with the current style. The M16A1
did not receive a fully chromelined bore until 1970 or so. The Army
adopted the M16A1, while the Air Force continued to use the M16. both
designs served at the same time and both continued to receive product
improvements as Colt designed them. The only difference between the two
was the presence of a forward assist, or not.
By 1968, the M16's major faults seemed to have been worked out and it
was quite popular with the troops for the most part. They liked its
lightweight, compact size, and the ability to carry large amounts of
ammunition. Though many still wished it had greater range and stopping
power. Nevertheless, most soldiers asked at the time preferred the M16
over the older M14, especially those in Vietnam. In 1969, Colt finally
created a reliable 30 round magazine for the M16, but these were slow to
make their ways over to Vietnam and in fact the 20 round magazine was
not phased out until 1976 or so. By 1968, the M16A1 had become the
established and tested firearm that would remain the standard issue in
the US military for two decades. Even today, many question if the M16A2
is really an improvement over the A1.
Parts Transition Timeline (incomplete and I might have some dates off by a year or so)
1960: Model 01 in production, cast FSB, Winchester made barrel with WW
mark, metal front sling swivel with rollpin, Green painted furniture,
1963: Model 02 in production, change from original duckbill FH to
improved 3 prong, barrel twist rate increased from 1in14 to 1n12, barrel
marked VP, furniture is black, change from original fathead to improved
flathead firing pin,
1964: Models 603 and 604 in production, cast FSB to smooth forged, early
to A1 dustcover, M added to barrel mark for magnetic particle tested,
front sling swivel was rubber coated and riveted, rear sling swivel is
rubber coated, forward assist first appears, change to modern type of
1965: CAR15 family in production, first GX series carbines,
1966: XM177 series in production, M VP to MP marked barrel, Edgewater buffer to current standard buffer,
1967: M16A1 rollmark appears, 3 prong FH to A1 FH, carbon steel gas tube
to stainless steel, chromed chamber, drain hole added to FSB,
1968: H&R & Hydramatic manufactured M16s appear, 'drain' hole handguards,
1969: barrel marking to C MP C, current style of gas tube appears,
1970: FSBs are not smoothed-have 'flash' from forging,
1971: barrel has both chromelined chamber and bore with C MP B mark, A1
buttstock appears with trapdoor for cleaning kit & fixed metal sling
1974: C MP B to C MP ChromeBore on barrel,
the Early Carbines (605 & 607)
The rifle length M16 was not the only AR-15 in the jungles of Vietnam.
Shortly after Colt acquired the rights to the AR platform, it began
developing a line of shorter and lighter carbines, to equip special
forces and for special missions. The first of these was the 605, which
appeared in 1964. This model was nothing more than a standard XM16E1
with the 20" barrel cut down to 15". It had the bayonet lug milled off
usually and used the then standard 3 prong flash hider. Lower receiver
was E1type and buttstock was the same as on a standard rifle. Early
upper receivers did not have forward assists, though some late models
had a milled off FA housing. The 605 was shorter than a standard M16
true, but was plagued with reliability issues because of virtually no
dwell time between the gas port and muzzle. It never occurred to Colt to
increase the port's diameter it seems. This was not a very successful
model, but is notable for being the first AR-15 carbine. Very few 605s
made their way into the hands of soldiers, though a few ended up with
The 607 was Colt's next attempt at an AR carbine in 1965. Interestingly,
in Colt's catalogue, the 607 was listed as a submachinegun; not a
carbine. Though the weapon was as compact as some SMGs of the day, it
still fired a rifle cartridge. By modern standards it remains a carbine.
It seems clear this was just a marketing ploy by Colt. It was
moderately more successful than its predecessor. In many respects, this
model layed the ground work for the modern carbine: 7" long 'carbine'
length gas system, 10" barrel, 'carbine' length buffer tube, and
collapsing stock were all found first in this model. Still, the 607 was a
transitional carbine. Its collapsing stock was made from a cutdown E1
stock and its handguards were also cutdowns from standard rifle triangle
types. The custom built furniture meant the carbine was time consuming
and expensive to make. The 10" barrel drastically decreased the weapon's
length, but had excessive muzzle flash, noise, and decreased
reliability. Early examples were fitted with the standard 3 prong flash
hider, but later ones had a 3.5" moderator installed. This moderator
controlled flash somewhat, helped with sound a bit, and increased
back-pressure. It did not have flash hider slots at the end like later
moderators would. Early 607s used slick-side upper receivers with no
forward assist, but later production ones were equipped with the assist
feature. It seems colt built these carbines from whatever was on hand,
including some cutdown pistol grips originally meant for the cancelled
608 air Force survival rifle. The carbine saw some service with Navy
SEALs under the designation of GX5857. I have no idea why it received
that designation or even what it really was supposed to mean. Its a very
unusual name for a US military firearm, even an experimental one. it is
not known for sure how many 607s colt produced but it was a small
number, probably 200 or less. This carbine was the first step on the
road which would one day lead to today's M4A1 Carbine.
the CAR-15s (XM177E1, XM177, & XM177E2)
The XM177 series saw the most widespread use throughout the Vietnam War
and afterwards in the US military. Behind the M4, these carbines are
probably the most recognizable Colts ever produced. In reality though,
rather few were actually fielded. The Colt 609 and 610 were introduced
in 1966. The only difference was that the 609 had a forward assist and
the 610 did not. In June of 1966, the Army ordered 2,815 609s and
designated them XM177E1. The 610 was given the label XM177 or GAU-5/A in
Air Force service. The XM177 had a 10" barrel like the previous
carbine, the classic 2 position CAR collapsing stock made of aluminium,
the same gas system and buffer as the 607, and used an E1 style lower
receiver. The XM's handguards wereof a new round type, which were both
easier to produce than the triangular style and stronger. Originally it
was issued with the same 3.5" moderator, but later received a new 4.3"
moderator which also doubled as a flash hider. The XM177E1 was an
improvement over the GX5857, but still suffered from excessive muzzle
flash and less than ideal reliability.
In 1967, Colt began offering the 629/630 model (forward assist or no
forward assist). The 629 featured a longer 11.5" barrel which made the
carbine more accurate, more reliable, and decreased muzzle flash a bit.
The extended barrel also made room for the XM48 grenade launcher
attachment so a grenade ring was installed on some models to accommodate
the unit. The 4.3" moderator was standard on the new model and it used
the new A1 lower receiver and chrome lined chamber. In most other ways
the 629 was the same as the 609. In April of the same year, the Army
purchased 510 629s and designated them as XM177E2. A short time later
the Air Force also acquired the new carbine and gave it the label of
GAU-5A/A. The 629 would be Colt's last 10/11" carbine and the final
version. Though it was more reliable and userfriendly than previous
AR-15 carbines, not all of its problems were ever resolved. It was still
not 100% reliable and known for being picky about which ammunition it
would cycle. It still had a loud report and flash, even with the
moderator. On the other hand, it was very compact, light, and easy to
use. Some of the very first 30 round magazines went to the XM177s being
used in Vietnam. They were very popular with special forces and soldiers
out on point. Production only lasted a short time, with the final
XM177E2s being manufactured in 1970. In many ways, it was the last of
the true classics commonly called a CAR-15. Many would remain in service
for decades,especially with the Air Force.
the M16A2 (701 & 705)
The replacement for the M16A1, the M16A2, was a long time in coming. Its
roots stretch back to 1970, when it was decided that 5.56mm would
become a standardized NATO caliber. This would greatly help with supply
legistics in Europe in the event of war. Trials to select a standard
loading of the 5.56mm NATO cartridge began in 1977 and concluded in
1980, with FN's 62g M855 being agreed upon. The M16 magazine also became
an unofficial NATO standard magazine type. The new projectile performed
best out of a 1 in 7 twist barrel, so a new service rifle was called
for in the US military. The Colt 701 and 705 were the results.
In 1982, the military officially adopted the Colt 705 as the M16A2. The
push for this configuration was mostly from the Marines who wanted a
more accurate and long ranged weapon, though all services accepted it.
Issuing of the A2 was delayed until 1986, due to budgetary constraints
and with some units even as late as the 1991 Gulf War. The M16A2
differed from the M16A1 in many ways. First of all the barrel was made
heavier out past the front sight base to give more strength and accuracy
during sustained fire. It featured the new 1 in 7 twist for the M855
bullet. The 20" length was kept however and it was still skinny under
the handguards. A new 5 slot flash hider combination muzzle brake was
introduced; as well as new round handguards taken from the XM177 series
and lengthened to fit a rifle. A tapered delta ring was added to retain
the handguards, which was easier to use during disassembly. The rifle
had a new rear sight which was now adjustable for both elevation and
windage, and the front sight was also updated. the Forward assist button
was redesigned from the traditional 'tear drop' shape, to a round
style; and a brass deflector addded to make the rifle more left-hand
friendly. Both the front and rear sections of the lower receiver were
reinforced. Pistol grip was redesigned with a new finger groove and the
useless sling swivel point at the base was removed. The ejection port /
dustcover door was changed to make it easier to grab and close.
Buttstock was lengthened by 5/8", given a new texture, and more
aggressive checkering on the buttplate. The M16A2 (705) had a 3 round
burst mode instead of full auto. The M16A3 (701) on the other hand
retained the M16a1's full-auto fire control group. Mostly the military
purchased the A2 model. The new rifle was more accurate, more durable,
and more comfortable for many shooters. The new features did come at the
price of added weight however. Also, the A2's rear sight is more
succeptable to damage than the A1's more basic sight. The 30 round
magazine became standard issue with the M16A2 as well.
Today the M16A2 is being replaced by the M16A4. Essentially, the A4 is
no more than an A2 with a removable carry handle. Under the handle is a
standard 1913 rail for the mounting of optical devices. Some of the
latest rifles also have a thicker barrel profile under the handguards.
Colt's 905 is the A4 with 3 round burst FCG, while the 901 features a
full-auto mode instead. Regardless, the new series has long developed
past the platform's teething problems. The A4 serves along side the M4
carbine, as the standard front line issue small arm in our military
the Development of the M4 Carbine (653 through 933)
The M4 Carbine is one of the most recognizable and famous variants of an
already highly recognized and famous firearms family. It can trace its
roots right back to the earliest Colt carbines like the 607 and 629. It
is rather hard to say exactly when the M4 came into existance as it grew
out of several developments.
In the 1970s, the military purchased a few commercial colt 653 carbines
to replace wornout or damaged XM177s. The 653 was not much more than a
629 with a 14.5" barrel and an A1 flash hider. The added 3" of barrel
increased the carbine's reliability and also allowed it to mount a
bayonet. Almost by accident, Colt stumbled upon the best barrel length
for a military carbine. With a 14.5" barrel, the 653 wasn't much longer
than a 629 with its 4.3" moderator, it was more accurate, and not much
heavier. This carbine is now days commonly referred to as the M16A1
The next Colt carbine of note was the 723, which came about in the early
1980s. The 723 featured a thin profile 14.5" barrel, but with the then
new 1 in 7 twist rate. It had a brass deflector and round forward
assist, but retained the a1's sights. Most 723s had 3 round burst mode
instead of full-auto. It is commonly referred to as the M16A2 Carbine
and indeed was designed to be a companion to that rifle. One might also
call this carbine a pre-M4 or even XM4. Please note several variants of
this carbine were produced. In addition, Colt seemed to use whatever
parts were on hand. So some 723s were built on A1 lowers and some on a2.
Some had tear drop forward assists, though the round type was
'standard' if that can be said of something like this. It still had the 2
position collapsing CAR stock found on the first Xm177s. Some of these
carbines were purchased by the military and could be considered a 'Black
Hawk Down' carbine, but again, its hard to pin point anything for sure
with a series 700 carbine. Features could wildly vary. The Air Force
updated some of their older carbines with the new 1 in 7 twist barrel
and re-labeled them GUU-5/P. The GUU could be made by rebarreling an
existing firearm, or installing a complete new upper. The 727 version
had a barrel with the cut or step to allow the M203 grenade launcher to
be mounted. This feature would soon be standard on the M4.
In 1994, the Colt 920 was officially adopted into military service as
the M4 Carbine, though of course it has taken years for it to be fully
deployed. The first versions of the M4 had fixed A2 carry handles, but
most today have removable handles with rails underneath like the M16A4.
The carbine shares an 80% parts commonality with the M16A2 as well.
Originally, it was meant to replace both the M3A1 Grease gun and Beretta
M9 pistol in some units, but since then it has been decided to make the
carbine general issue to most soldiers. Before the M4 came along in
fact, officially Marine officers were issued only pistols (the 1911 and
M9). The M4 has a 3 round burst mode and the M4A1 is capable of
full-auto fire. Both can accept the M203 grenade launcher. Barrel is
14.5" long, 1 in 7 twist, with the M16A2 profile: thin under the
handguards and heavy past the front sight base. Recently, Colt has
released the 921HB, which has a heavier barrel under the handguards. The
carbine can mount a bayonet. New handguards were also designed for the
carbine with maximum heat dissipation in mind. The handguards are of a
new ovular shape with double steel heatshield inserts. Both the A2 flash
hider and pistol grip are standard. Finally with the M4, Colt stopped
using the old 2 position CAR collapsing stock. The new M4 stock has 4
positions and has been reshaped with 2 sling attachment points. the
front sling swivel is now on the side and can be reversed for either
right or left side. The M4 uses the same 7" gas system and carbine
length buffer first featured on the GX5857 though.
In its original intended roll, the 920 is rather capable, but it is not
wellsuited for sustained fire fights. The short gas system tends to
overheat due to its high rate of fire. Also, because of the 14.5"
barrel, the carbine has a limited effective range. I would assert that
the problem does not lay with the weapon system itself, but rather how
it has been deployed. There are some situations inwhich the M16A4 is
called for and some where the M4 is best. There will never be a
one-size-fits-all military small arm.
Even though after the XM177 series, the 14.5" barrel length became
popular, Colt did not entirely abandon the 11.5" and even 10" length
carbines. The 733 or M16A2 Commando is similar to the M16A2 Carbine, but
with a 11.5" barrel. The 733's barrel could be A1 thin or A2 heavy,
but always has a 1 in 7 twist rate. Normally it would have a1 sights,
but the rest of its features would be A2. The CAR style stock could be 2
position or 4 position, but seems to have always been made of polymer,
not metal. Most of the time the Commando can be found with a full-auto
FCG. This configuration found favor with special operations teams and
law enforcement. It was short, light, and easy to maneuver in a room.
Colt finally figured out that in order to insure reliable cycling with
an 11" barrel, the gas port needed to be enlarged. Still, it had limited
range and limited application.
Next came the 933 or M4 Commando. Essentially, the 933 is an M4 carbine
but with a 11.5" barrel. It can come from the factory with either a
fixed carry handle and A2 sights, or a flat-top receiver and removable
handle. It has a heavy profile barrel and 4 position collapsable M4
style stock. The 933 has found favour with the Navy SEALs, like its
distant ansester, the 607. Its the M4 Commando that has been the basis
for the newest carbine used by the Navy, the Mk 18 Mod 0. The Mk 18 has a
10.3" barrel if made by Colt or 10.5 if by LMT. It is designed to be
highly customizable for any mission and many tweeks have been made to
insure reliable operation. Nevertheless, with such a short barrel, it
will never be as reliable as an M16A2 rifle or even an M4 Carbine. It is
very compact though.
Colt SP1 in 602 configuration
The SP1 has a mfg date of 1974. I have modified it in several ways:
1) Replaced original cut SP1 bolt & carrier with original chrome slick side carrier with original chromed bolt.
(bolt group with milled retainer but modern firing pin)
2) Installed early bolt group parts including improved flat-head firing pin and early milled type retaining pin.
3) Replaced the 'Red Wine' standard rifle buffer with an original Edgewater buffer.
(strictly speaking, the Edgewater is a 'spring guide' not a true buffer)
4) Replaced A1 style buttstock with an early Type D XM buttstock with no trap door and rotating sling swivel.
5) Used a buttstock screw without drainhole.
6) Replaced handguards with early ones that do not have what are commonly called 'drain' holes.
7) Installed original 3 prong flash hider
8) Used an early style wide lock washer behind the flash hider.
9) Installed Nodak repro early triangle charging handle
10) Installed 602 'skinny' pistol grip.
11) Replaced the Colt SP1 front screw with a 601 style takedown pin with
ball detent. This is a compromise and closer to an original but not
12) I bought a Nodak reproduction 20 round 'Waffle' magazine, but its not in the pictures.
The M1 style cotton sling is appropriate for an early 602 and is
original. I'd like to find an earlier barrel without chromelining and
smooth FSB with no drain hole. Other than that, i feel quite good about
this build being a relatively accurate reproduction of a 1965-1966 XM16
An older picture with it on the bipod.
Early cleaning kits were kept in the pouch with the detachable bipod.
605 style upper on Nodak A1 lower
Early style carbine upper with a 16" barrel instead of 15" for legal
reasons, 3 prong flash hider, slick-side upper receiver, and all chromed
bolt carrier. In the pictures its on my Nodak A1 lower, but it will
have a perminant home on an XME1 lower with 607 1st generation
collapsing stock. I am doing a 605 meets 607 early retro carbine build,
but the stock isn't made yet and Nodak needs 2 more weeks on the lower
Update: i did finish this build but ended up parting it back out and
making my money back and then some. It was fun to do, but I was getting
too many ARs hanging around.
Colt M16A1 Upper on Nodak A1 lower
Colt M16A1 complete upper on a Nodak A1 lower receiver with a standard
Type E A1 buttstock. Sling is the mid-generation 'seatbelt' style used
in between the cotton sling and later silent sling.
XM177E2 Upper on Nodak A1 lower
It took me roughly a year to complete this project and during that time
some parts were swapped around, including the lower which started as an
NDS E1 and ended up an NDS A1. Its as close to an original XM177E2 as i
could make it without going crazy and spending an insane amount of
money. Its actually closer to a Colt 639 than a 629 because of the flat
slip ring and later style of FSB and receiver. No matter. Here are the
parts i used:
1) Nodak M16A1 XM grey lower receiver
2) Colt M16A1 upper receiver and slip ring from an Apex parts set. I also used some of the lower parts.
3) Colt surplus M16A1 bolt group
4) JT lightweight 11.5" non-chromelined barrel with the bayonet lug
removed from the FSB and the sling swivel installed with a rollpin.
5) Essential Armss XM177 style aluminium buttstock with standard tube
and earlier style of retaining nut with standard carbine buffer.
6) original Colt 1970s 'shiny' 6 hole handguards with single heatshield.
7) standard A1 pistol grip.
8) standard A1 front sight post and standard carbine gastube.
9) 5.5" extended XM177 6 slot flash hider. This part i agganized over. I
tried very hard to use a Brick repro XM moderator and grenade ring, but
no matter how i did it, i couldn't get the overall length right. It was
too short with just these pieces and a lockwasher, and too long with an
extension piece and looked awful. Eventually i just gave up and used a
normal 5.5" flash hider and discovered at least one benefit; its a lot
lighter! Its now perminantly installed.
10) standard 2 point GI web sling to complete the look.
Colt M16A2 Upper on ATM lower
Colt M16A2 upper on a generic A2 lower with proper A2 buttstock and pistol grip.
Colt LE6520 Carbine
The 6520 is basically a semi-auto only version of the M16A2 carbine. It
has a lightweight 'pencil' 16" barrel but with the 1 in 7 twist rate. It
has CAR style handguards, but an M4 buttstock. It uses a standard A2
Update: I never did keep one of these, though I think they are very
handy little carbines. The one in the pictures ended up being split into
upper and lower, with the lower legally exported up to Canada.
Colt LE6920 Carbine
Standard Colt 6920, the semi-auto only version of the M4 carbine. Has a
16" barrel instead of 14.5" but has standard M4 furniture, upper
receiver, bolt & carrier, and standard pin sizes.
Well, that is all I have for now. Just thought we'd take a trip down M16
memory lane. Retro builds to me are really enjoyable and rewarding. In
the future, i might do more, but who knows? So lets share some Vietnam
era Ars or just any classic / retro AR builds you might have kicking
around. Surely even you are a little tired of seeing rails and high
dollar optics aren't you?
Click here for the Ozark Bear Arms Gunbroker auction page!