Country of origin
40 x 46 mm
Cyclic rate of fire
Practical rate of fire
Range of effective fire (grenades)
Maximum range (grenades)
Range of effective fire (buckshot)
The AAI M203
is the primary grenade launcher of the US armed forces, and was the
first weapon of this type to achieve operational service. It has
been long-lived in operational service, and both used and produced
in many nations.
The background of the M203 is inter-tangled with those of
many other projects and weapon systems. It was developed in response
to the GLAD (Grenade Launcher Attachment Development) program, which
was intended to provide the US Army with an underbarrel grenade
launcher for use on the Colt XM16E1 assault rifle (which soon
entered service as the
much more difficult task than it sounds today, as at the time, no
such weapon had ever been developed in the US. The GLAD program and
the M16 were both offshoots of Project SALVO, which had originally
been planned in 1951 to produce a multi-barrel assault rifle that
fired flechette projectiles at tremendous rates of fire. GLAD was
preceded by another SALVO offshoot, Project Niblick, which produced
the 40x46 mm low-velocity grenade later needed for the GLAD weapon. Niblick also ultimately resulted in the development of the
grenade launcher that preceded the M203.
Project Niblick didn't end with the M79, and it was from this
program that the GLAD requirement arose from --- though despite
being considered a distinct program, it was tied directly to Project
SALVO, as there were three competing rifle designs, and three
competing grenade launchers. After being formalized in 1964, three
competing weapons were submitted by the industry to the GLAD
program; one by Colt, one by H&R, and one by AAI. The Colt CLG-4 was
declared the winner and type-classified as the XM148 (not to be
confused with the earlier Springfield Armory T148, which was a
precursor to the M79), and Colt was contracted in July of 1966 to
produce 20 000 of them for field trials in Southeast Asia. The first
XM148s arrived in South Vietnam that December.
However, the US Army quickly regretted that decision. The
Colt XM148 proved to be a disaster in actual combat conditions. It
was prone to accidental discharges, was extremely laborious to field
strip and clean, had numerous tiny parts that were easily lost in
the field, and too heavy a trigger pull. This weapon was quickly
pulled from service, and the Army soon reversed their decision in
the GLAD program, awarding AAI a contract to build their grenade
launcher after all. It was type-classified in November of 1968 as
the XM203, and a month later the Army awarded AAI a contract to
produce 600 of them for testing in Southeast Asia (apparently, the
Army's enthusiasm for exceptionally large initial orders was blunted
by the failure of the XM148). Though later testing would reveal
problems in arctic conditions, the XM203 performed well in Vietnam,
and it was formally adopted into operational service with the US
armed forces in 1969.
In appearance, the M203 more closely resembles *part* of a
weapon than a complete weapon (which is not far from the truth, as
it must be mounted on another weapon to use it). It consists of a
long, partially-ribbed tube attached to a support rail above, and a
trigger group aft. The aft ribbed portion of the barrel slides over
the front of the barrel when the weapon is reloaded, and the chamber
is located in this forward section. The upper rail not only supports
the barrel, but is also used to attach the M203 to another weapon.
It is impossible to operate the M203 successfully unless it
is attached to a larger weapon, usually an assault rifle. There are
exceptions to this rule though; for example, variants of the
submachine gun. In US military service, the M203 is attached to an
M4. Attaching the M203 to a weapon is a procedure requiring
only 5 minutes, and the only tool required is a screwdriver.
There are no sights on the M203; these must be fitted to the
weapon that the launcher is attached to. Otherwise, the only
reference with which to aim the launcher is the user's best guess.
The sights fitted to the main weapon consist of a front leaf and a
rear ladder, with settings from 50 m to 250 m in 50 m increments.
To fire the M203, the operator must first unlock the barrel
assembly via the barrel latch on the top-left side of the weapon,
and slide the barrel assembly forward, and then backward, which
cocks the weapon. The rear barrel assembly is then slid forward
again, exposing the chamber; if an unfired round or a spent casing
are in the chamber, it will be automatically extracted and ejected.
A round may now be loaded into the chamber, and the slide drawn
back. If completed properly, the extractor will catch the rim of the
casing. The barrel is then locked into its fully-closed position by
re-engaging the barrel latch, and the M203 may now be fired by
simply pulling the trigger.
The M203 may be fired from the shoulder in standing,
kneeling, or prone positions. There is no backblast hazard, and a
minimal muzzle blast hazard, allowing the weapon to be safely fired
from any confined space. The weapon bearing the M203 may also be
braced with its buttstock against the ground and the muzzle aimed
upward, allowing the M203 to be used like a mortar. This is best
accomplished from a sitting or prone position. It is also possible
to fire the M203 from the hip, but accuracy will suffer accordingly.
As it is mounted under the front of a larger weapon, the M203 cannot
be fired one-handed like a pistol, as with the
A number of operational hazards in operating the M203 have
also been identified, including reliability problems in severe cold
conditions (though the M203's cold weather problems have since been
remedied), and the omission of a safety mechanism. A now famous
quote from a US Army preventative maintenance magazine also states,
"A slipping gear could let your M203 grenade launcher fire when you
least expect it. That would make you quite unpopular in what's left
of your unit.".
The grenades fired by the M203 are the same as used in the
M79; see the page on that weapon for a brief description of some of
The M203 first saw combat during the Vietnam War, in which it
was deemed a great success. It has since been used by many nations
in seemingly innumerable conflicts all over the world, also usually
In addition to AAI
Corporation, numerous other US companies have produced
M203s under license, including Knight's Armament, Bushmaster, Airtronic USA, R/M Equipment, US
Ordnance, the Lewis Tools &
Machinery Company, and --- ironically --- Colt Defense. AAI
themselves only produced 10 000 M203s, before passing-on production
to these other companies. It has also been manufactured abroad by
Colt Canada and Diemaco in Canada, Daewoo in South Korea, the Floro
International Corporation in the Philippines, and Maadi in Egypt.
MKEK in Turkey manufactures the T-40, a variant of the M203.
The M203's operators include Afghanistan, Albania, Australia;
Austria; Bangladesh, Brazil, Brunei, Cambodia, Cameroon, Canada,
Chile, Columbia, the Czech Republic, Denmark, the Dominican
Republic, Ecuador, Egypt, El Salvador, France, Gabon, Greece,
Honduras, India, Indonesia, Iraq, Ireland, Israel, Italy, Japan,
Jordan, Kuwait, Lebanon, Liberia, Malaysia, Mexico, Morocco,
Myanmar, the Netherlands, New Zealand, Oman, Pakistan, Panama, the
Philippines, Portugal, Qatar, Saudi Arabia, Singapore, South Korea,
Sri Lanka, Sweden, Thailand, Turkey, the UAE, the UK, the US, and
The M203 is still produced by its various manufacturers,
even now after over 50 years of continuous mass production. New
example costs between $1 000 and $2 000.
In US service, the M203 is slated to be replaced in the 2020s
by the M320, another 40 mm underbarrel grenade launcher.
Original production model. It can be mounted on the M16A1, M16A2, or
M16A1, but not on an
M4 or an
M203A1: Shorter M203 for use on carbines, such as the
It has a shorter 229 mm barrel.
M203A2: Improved M203 for use on the M16A4. Using the M5 MWS
Rail System, it can also be attached to an M16A2.
M203 DAX: Improved M203 with a double action trigger, and a
resized chamber that will accommodate a variety of less-lethal
M203PI: A modified M203A1 for use on a wide variety of other
rifles. For example, the Irish Army employs the M203PI on the
AUG, which is too short for a standard M203, and won't accept
K201: M203 built under license in South Korea by Daewoo.
FIC M203: M203 built under license in the Philippines by the
Floro International Corporation.
T-40: Turkish grenade launcher based on the M203,
manufactured by MKEK.
SPG-1: M203 built under license in Indonesia by PT Pindad.
Gk M/98: Danish designation for the M203.
Chinese 35 mm underbarrel grenade launcher for use on a variety of
rifles. It is similar in concept to the US M203. Sometimes it is
referred as the Type 91. There are numerous version of this weapon,
including a standalone and vehicle-mounted versions.
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