M203 grenade launcher

The M203 is a single shot 40 mm grenade launcher that attaches to a number of popular assault rifles, but was originally designed for the U.S. M16 and its variant, the M4 Carbine. In the U.S. military, when a rifle or carbine is equipped with the launcher, both weapons are collectively referred to as an M203. The launcher can also be mounted onto a C7, a Canadian version of the M16 that uses an optical scope instead of an iron sight, and requires the bottom handguard on the rifle to be removed in order to mount the launcher. Stand-alone variants exist as do versions capable of being used on many other rifles. The device attaches under the barrel and forward of the magazine, the trigger being just forward of the rifle magazine. The rifle magazine functions as a hand grip when firing the M203. A separate sighting system is added to rifles fitted with the M203, as the rifle's standard sights are not matched to the launcher. The version fitted to the Canadian C7 has a sight attached to the side of the launcher, either on the left or right depending on the user's needs.

History
The M203 was the only part of the army's flechette rifle project to go into production. The M203 has been in service since 1969 and was introduced to U.S. military forces during the early 1970s. Replacing the older M79 grenade launcher and conceptually similar Colt XM148 design. However, while the M79 was a stand-alone weapon (and usually the primary weapon of troops who carried it), the M203 was designed as an under-barrel system attached to an existing rifle. Because the size and weight of 40mm ammunition limits the quantities that can be carried on patrol, and because a grenade is often not an appropriate weapon for a given engagement (i.e. when the target is at close range or near friendly troops), an under-barrel system has the advantage of allowing its user to also carry a rifle and to easily switch between weapons.

It is sometimes argued that the M203 was a poor replacement for the M79, as while the M79 was quick to reload and more or less accurate under adverse conditions, such as in the Vietnam War, the M203 was more difficult and awkward to operate.
A new grenade launcher, the M320, will likely replace the M203 in United States service eventually. The M320 features an advanced day/night sight, a double action firing mechanism(as opposed to the M203's single action) as well as other benefits such as an unobstructed side-loading breech.

Uses
The M203 Grenade launcher was intended to be used as close fire support for point and group area targets. The round is designed to be effective at penetrating windows, blowing up doors, producing casualties in groups of enemies, destroying bunkers, and damaging or disabling non-armored vehicles. A well trained 203 gunner can also use his weapon to suppress the enemy, both from movement and sight. In addition, the M203 can be used as a crowd control weapon when equipped with the M651 Tactical CS grenade. The M203 was not, and is not intended to be used against armored or heavy vehicles.

Rounds
The M203 is able to fire a variety of different rounds for many purposes. There are 8 different rounds for the M203:

M406 High-Explosive round. Often called the 'H-E' round, this round is intended to produce kills and casualties on point and group targets, as well as destroying bunkers and doors. This round has a 5 meter 'kill zone' and a 15 meter 'casualty zone'.

M433 High-Explosive Dual Purpose round. Able to penetrate 2 inches of steel when fired straight at the target, it is designed to produce casualties and kills. This round has a 5 meter 'kill zone' and a 15 meter 'casualty zone'.

M585 White Star Cluster. Used for Signaling and Illumination at night time.
M651 Tactical CS Grenade. Used for crowd and riot control, the round releases large amounts of CS gas to disable and scatter crowds.

M781 Practice round. Used for zeroing and qualifying on the M203. The tip is filled with orange chalk that creates a cloud on impact, allowing the spotter and scorer to see where the round hit.
Star Parachute. The White (M583A1), Green (M661), and Red (M662). Used to the same effect as the Star Cluster round for signaling and illumination purposes.

Ground Marker. The Red (M713), Green (M715), and Yellow (M716). Used as a signaling smoke grenade round to mark soldiers and targets.

Buckshot - Used for room clearing and point blank firing. Much like a very large shotgun shell.
Except for the Star Cluster and Star Parachute, all 40MM Grenade rounds are impact detonated. In addition the rounds have a minimum arming distance of 14 to 27 meters, and firers are advised to fire at targets more than 50 meters, the minimum safe stand off distance from an explosion.

Components
The M203 Grenade launcher system comes with a variety of components, usually including the launcher, adaptors for attachment to assault rifles, and leaf sights (which can be used with the rifle's front sight post). M203s can also come with quadrant sights, mounting to a MIL-STD 1913 Rail, or to the carrying handle of an M16 rifle.

Variants
There are numerous variants of the M203 manufactured in the U.S., and throughout the world, for various applications. These vary chiefly in the length of the barrel, attachment type, and quick detach (QD) capability.

The standard M203 is intended for permanent (armorer level) attachment to the M16A1, M16A2 and M16A3 rifles, and utilizes a 12" rifled barrel. These can also be attached to M4 and M4A1 carbines, using a different front attachment point forward of the front sight block, but the SOPMOD kit uses M203A1 grenade launchers.

The American M203A1 is intended for use with the M4 and M4A1 Carbine. The barrel is shortened to 9", and principally the M203A1 QD is able to quickly detach from the rifle, and be replaced by a Knight's Armament Company M4 RAS lower handguard. An advantage of using a 40 mm grenade launcher on an assault rifle equipped with MIL-STD 1913 Rails is the attachment of various range-finding optics.

The Canadian M203A1 by Diemaco (now Colt Canada) is a similar design with a different mounting system that does not require mounting points of the same profile as the M16A1 rifle's. The weapon's 9" barrel slides forward further than the standard American models to allow longer rounds to be loaded. This model is identifiable by the increased distance between the grenade launcher's barrel axis and the rifle's. This weapon may no longer be in production, but is still in use.

The M203A2 is intended for use with the M16A4 MWS (Modular weapon system). Using standard 12" barrels, the grenade launcher is intended for use in concert with the Knight's Armament Company M5 RAS. Again, an advantage of this system is the attachment of range-finding optics makes precision targeting easier.

The M203 PI system is used for attachment of the M203 to other rifles, including but not limited to the Steyr AUG, H&K G3 and other rifles, and even the MP5 submachine gun. Most of these other companies have since devised 40 mm grenade launchers custom integrated with the weapon.

The M203 and M203A1 are currently manufactured by Airtronic USA, Inc. of Elk Grove Village, Illinois for the U.S. Department of Defense under contract numbers W52H09-06-D-0200 and W52H09-06-D-0225. Each contract is for up to 12,000 units. Each unit is shipped with hand guard, leaf sight and quadrant range sight. The contracts unit prices vary from $840 to $1,050 each. The production rate is 1,500 units per month. The M203 PI is manufactured for both U.S. Department of Defense and for commercial sales (to Law Enforcement agencies both in the USA and abroad, and for foreign military sales) by RM-Equipment Inc. of Miami, Florida.

AT4

The AT4 (also variously AT4 CS, AT4-CS, AT-4CS or just AT-4; an alpha-phonetic word play on the weapon's calibre of 84 mm[citation needed]; "CS" represents "Closed (or 'confined') Spaces" referring to the rocketry being designed to operate effectively from within buildings in an urban environment. ) is a portable one-shot anti-tank weapon built in Sweden by Saab Bofors Dynamics (previously Bofors Anti Armour Systems). In the U.S. and NATO inventory, it replaced the M72 LAW (Light Anti-armor Weapon). Saab has had considerable sales success with the AT4, making it one of the most common light anti-tank weapons in the world. It is intended to give infantry units a means to destroy or disable armored vehicles and fortifications, although it is not generally sufficient to defeat a modern main battle tank (MBT). The launcher and projectile are manufactured prepacked and issued as a single unit of ammunition, rather than as a weapon system, with the launcher discarded after a single use.




Development
The AT4 is a development of the 74 mm Pskott m/68 (Miniman), adopted by the Swedish army in 1960's. Like the m/68, the AT4 was designed by Försvarets Fabriksverk (FFV) and manufactured at their facility at Zakrisdal, Karlstad, Sweden.

Even before the AT4 had been adopted by Sweden, it participated in a competition for a new anti-tank weapon for the U.S. Army. Runners up were the AT4 and the German Armbrust. Though impressed with the AT4, the US Army saw room for improvement, specifically the sights and slings, which were redesigned. Thereafter, the AT4 was adopted by the U.S. Army as the M136. The Swedish army recognised these improvements and subsequently adopted the Americanized version of the AT4 as the Pansarskott m/86 (Pskott m/86).

In the early 1990s, there were tests of a tandem charge 130 mm version (Bofors AT 12) that would be able to penetrate the front armor of any modern main battle tank (MBT). However, the project was canceled due to the dissolution of the Soviet Union and cuts in Western defense budgets.

Operation
The AT4 operates on the principle of a recoilless weapon, meaning that the forward inertia of the projectile is balanced by the mass of propellant gases ejecting from the rear of the barrel. Since the weapon generates almost no recoil, a relatively large projectile can be fired which would otherwise be impossible in a man-portable weapon. Additionally, the barrel can be designed to be very lightweight as it does not have to contend with the extreme pressures found in traditional guns. The disadvantage of this design is that it creates a large "back blast" area behind the weapon which can cause severe burns and overpressure injuries both to friendly personnel in the vicinity of the user and sometimes to the user himself. This makes it difficult to employ in confined areas.

he problem of back blast has been mitigated recently with the AT4-CS (Confined Space) version, specially designed for urban warfare. This version uses a saltwater countermass in the rear of the launcher to absorb the back blast—the resulting spray captures and dramatically slows down the pressure wave, allowing troops to fire from enclosed areas.

To fire, the user must first ensure that no friendly troops or equipment are present in the back blast area. If firing from the prone position (i.e. lying on his stomach) he must also place his legs well to the side to avoid burning himself. He then disengages two safeties, cocks a mechanical firing pin and presses a trigger button. Aiming is accomplished via range-adjustable plastic sights, which are concealed beneath sliding covers for transport. Alternatively, the weapon can carry an optical night sight on a removable mount.

The AT4 requires little training and is quite simple to use, making it suitable for general issue. However, as the cost of each launcher makes regular live-fire training very expensive, practice versions exist which are identical in operation but fire reloadable 9mm or 20mm tracer ammunition. Both practice cartridges are unique to their respective weapons, with their trajectory matched to that of the live rocket. The 20mm version is also a recoilless weapon and is favored by the Swedish army because of the added realism of the back blast as compared to the "plonk" sound of the 9mm round (similar to the sound of a finger tapping on an empty can).

Specifications
Length: 101.6 cm (40 in.)
Weight: 6.7 kg (14.75 pounds)
Bore diameter: 84 mm
Maximum effective range: 300 metres (984.3 feet), although it has been used in excess of 500 meters for area fire.
Penetration: 400 mm of rolled homogeneous armour (RHA) (also see below)
Time of flight (to 250 metres): less than 1 second
Muzzle velocity: 285 metres (950 feet) per second
Operating temperature: -40 to +60°C (-40 to +140°F)
Ammunition: Fin-stabilized projectile with shaped charge warhead

FGM-148 Javelin

The FGM-148 Javelin is an American-made man-portable anti-tank guided missile fielded to replace the Dragon antitank missile.

Overview
Javelin is a fire-and-forget missile with lock-on before launch and automatic self-guidance. The system takes a top-attack flight profile against armored vehicles (attacking the top armor which is generally thinner) but can also take a direct-attack mode for use against buildings or fortifications. This missile also has the ability to engage helicopters in the direct attack mode. The missile reaches a peak altitude of 150m in top attack mode and 50m in direct fire mode. The missile is equipped with an imaging infrared seeker. The tandem warhead is fitted with two shaped charges: a precursor warhead to detonate any explosive reactive armor and a primary warhead to penetrate base armor. The Javelin was used in the 2003 Invasion of Iraq, with devastating effects on the Iraqi version of T-72s and Type 69 tanks.

The missile is ejected from the launcher so that it reaches a safe distance from the operator before the main rocket motors ignite; a "soft launch arrangement". This makes it harder to identify the launcher and allows it to be fired from within buildings; however, back-blast from the launch tube still poses a hazard to nearby personnel. Thanks to this "fire and forget" system, the firing team may move on as soon as the missile has been launched.

The missile system is carried most often by a two man team consisting of a gunner and an ammo bearer, although it can be fired with just one person if necessary. While the gunner aims and fires the missile, the ammo bearer scans for prospective targets and watches for threats such as enemy vehicles and troops.

Development
In 1983, the United States Army introduced its AAWS-M (Advanced Anti-Tank Weapon System - Medium) requirement, and in 1985, the AAWS-M was approved for development. In August 1986, the Proof-of-Principle phase of the development began, with three competitors designing prototypes such as the SC440-AT . In late 1988, the POP phase ended, and in June 1989, the full-scale development contract was awarded to a joint venture of Texas Instruments and Martin Marietta (now Raytheon and Lockheed-Martin). The AAWS-M received the designation of FGM-148.

In April 1991, the first test-flight of the Javelin succeeded, and in March 1993, the first test-firing from the launcher succeeded. In 1994, low levels of production were authorized, and in 1996 the first Javelins were deployed with US Army units.
Test & Evaluation

Development Test and Evaluation (DT&E) is conducted to demonstrate that the engineering design and development process is complete. It is used to reduce risk, validate and qualify the design, and ensure that the product is ready for government acceptance. The DT&E results are evaluated to ensure that design risks have been minimized and the system will meet specifications. The results are also used to estimate the system’s military utility when it is introduced into service. DT&E serves a critical purpose in reducing the risks of development by testing selected high-risk components or subsystems. DT&E is the government developing agency tool used to confirm that the system performs as technically specified and that the system is ready for field testing.

DT&E is an iterative process of designing, building, testing, identifying deficiencies, fixing, retesting, and repeating. It is performed in the factory, laboratory, and on the proving ground by the contractors and the government. Contractor and government testing is combined into one integrated test program and conducted to determine if the performance requirements have been met and to provide data to the decision authority.

In 1996 the General Accounting Office (GAO) published a report questioning the adequacy of Javelin testing. The report, called “Army Acquisition – Javelin Is Not Ready for Multiyear Procurement”, opposed entering into full-rate production in 1997 and expressed the need for further operational testing due to the many redesigns undergone.

Previously in 1995 the Secretary of Defense, William Perry, had set forth five new operational test initiatives. These included: 1) getting operational testers involved early in development; 2) use of modeling and simulation; 3) integrating development and operational testing; 4) combining testing and training; and 5) applying concepts to demos and acquisitions.

The late-phase development of the Javelin retroactively benefited from the then new operational test initiatives set forth by the Secretary of Defense, as well as further test conducted as a consequence of the Army’s response to the GAO report. Before the Milestone III decision and before fielding to 3rd Battalion 75th Ranger Regiment at Fort Benning (also Army Rangers, Special Forces, airborne, air assault, and light infantry), the Javelin was subjected to limited parts of the five operational test and evaluation initiatives, as well as a portability operational test program (an additional test phase of the so-called Product Verification Test) which included live firings with the full-rate configuration weapon.

Per initiatives and as a DT&E function, the Institute for Defense Analyses (IDA) and the Defense Department’s Director of Operational Test and Evaluation (DOT&E) became involved in three development test activities, including: 1) reviewing initial operational test and evaluation plans; 2) monitoring initial operational test and evaluation; and 3) structuring follow-on test and evaluation activities. The results of these efforts detected problems (training included) and corrected significant problems which led to modified test plans, savings in test costs, and GAO satisfaction.

Qualification testing
The Javelin Environmental Test System (JETS) is a mobile test set for Javelin All-Up-Round (AUR) and the Command Launch Unit (CLU). It can be configured to functionally test the AUR or the CLU individually or both units in a mated tactical mode. This mobile unit may be repositioned at the various environmental testing facilities. The mobile system is used for all phases of Javelin qualification testing. There is also a non-mobile JETS used for stand-alone CLU testing. This system is equipped with an environmental chamber and is primarily used for Product Verification Testing (PRVT). Capabilities include: Javelin CLU testing; Javelin AUR testing; Javelin Mated Mode testing; Javelin testing in various environmental conditions; and CLU PRVT.

The All-up-Round Test Sets includes: Extreme temperature testing; Missile tracker testing (Track rate error, Tracking sensitivity); Seeker/focal plane array testing (Cool-down time, Dead/defective pixels, Seeker identification); Pneumatic leakage; Continuity measurements; Ready time; and Guidance sections (Guidance commands, Fin movement).

Components
Missile
Warhead
The Javelin missile’s tandem warhead is a high-explosive antitank round. This round utilizes an explosive shaped charge to create a jet of superplasticity deformed metal formed from trumpet-shaped metallic liners. The result is a high velocity jet that can penetrate armor.
The Javelin counters the advent of explosive reactive armor (ERA). ERA panels lay over a vehicle’s main armor and explode when impacted by a warhead. This explosion does not harm the vehicle’s main armor, but causes steel panels to fly into the path of the antitank round’s jet, so that the jet expends its most potent energy cutting through the panels, rather than through the main armor. The Javelin uses two shaped-charge warheads in tandem. The precursor charge sets off the ERA and clears it from the path of the main charge, which then penetrates the target’s primary armor.

A two-layered molybdenum liner is used for the precursor and a copper liner for the main charge.

To protect the main charge from the explosive blast, shock, and debris caused by the impact of the missile's nose and the detonation of the precursor charge, a blast shield is used between the main and precursor charge. This was the first composite material blast shield and the first that had a hole through the middle to provide a jet that is less spread out.

A newer main charge liner produces a higher velocity jet. This change makes the warhead more effective as a penetrator and smaller, with more room for propellant to increase the missile's range.

Electronic arming and fusing, called Electronic Safe Arming and Fire (ESAF), is used. The ESAF system enables the firing and arming process to proceed, while imposing a series of safety checks on the missile. ESAF cues the launch motor after the trigger is pulled. When the missile reaches a key acceleration point (indicating that it has cleared the launch tube), the ESAF initiates a second arming signal to fire the flight motor. After another check on missile conditions (target lock check), ESAF initiates final arming to enable the warheads for detonation upon target impact. When the missile strikes the target, ESAF enables the tandem warhead function (provide appropriate time between the detonation of the precursor charge and the detonation of the main charge).

Propulsion
The system uses a soft launch to eject the missile from the launch tube. A launch motor fires within the launch tube but stops burning before the missile clears the tube so that the gunner is not burned by hot gases. The soft launch permits low recoil for shoulder launch. When the missile has cleared the launch tube and has traveled a safe distance, the main rocket motor ignites and the wings and fins flip out (as shown in the top-right picture) as the missile is propelled at the target at subsonic speeds.

The missile has an integrated launch and flight rocket motor which keeps weight low. The launch motor initiator ignites the launch motor igniter, which then ignites the launch motor propellant grain. Gases vent through the launch motor nozzle. After a delay, a signal is sent to the flight motor initiator which ignites the flight motor igniter to ignite the flight motor propellant. When enough gas pressure builds up in the flight motor chamber a burst disk (that separates the launch motor and the flight motor) ruptures. The flight motor gases flow down the launch motor chamber and out the launch motor nozzle.

For gunner safety, a pressure release system is used to ensure that a malfunctioning launch motor does not cause an explosion. The launch motor has shear pins that fracture in the event of launch motor overpressure and allow the motor to be pushed out the back of the launch tube.
An annular igniter is used for the launch motor. A circular ring design was key to integrating the launch motor and the flight motor. The launch motor igniter had to be placed in the nozzle so it could not be blown out the nozzle since debris would be a hazard to the gunner. The annular igniter allows exhaust gases to be vented.

The rupture or burst disc that separates the launch motor and the flight motor has a higher tolerance for pressure on the launch motor side and lower tolerance on the flight motor side. This allows the disc to protect the flight motor from the ignition of the launch motor and when sufficient pressure develops still let the flight motor rupture the disc and send flight motor gases past it and down through the launch motor chamber.

The launch motor propellant is the same as that used in other missiles. The flight motor propellant is derived from the propellant used in the tube launched.

Seeker
As a fire-and-forget missile, after launch the missile has to be able to track and destroy its target without the gunner. This is done by coupling an onboard imaging IR system (different from CLU imaging system) with an onboard tracking system.

The gunner uses the CLU’s IR system to find and identify the target then switches to the missile’s independent IR system to set a track box around the target and establish a lock. The gunner places brackets around the image for locking.

The seeker stays focused on the target’s image continuing to recognize as the target moves or the missile’s flight path alters or as attack angles change. The seeker has three main components: 1) focal plane array (FPA); 2) cooling and calibration; and 3) stabilization.

1) Focal plane array (FPA) - The seeker assembly is encased in a dome which is transparent to the FPA long-wave infrared radiation. The IR radiation passes through the dome and then through lenses that focus the energy. The IR energy is reflected by mirrors on to the FPA. The seeker is a two-dimensional staring FPA of 64x64 MerCad (HgCdTe) detector elements The FPA processes the signals from the detectors and relays a signal to the missile’s tracker.

The staring array is a photo-capacitive device where the incident photons stimulate electrons and are stored in the detector as an accumulated charge. The electrons are discharged, pixel by pixel, as currents to a readout integrated circuits attached at the rear of the detector. A better photovoltaic mechanism in which a voltage signal is developed directly from the impact of the photons and charge storage is done in the readout rather than in the detector material.

2) Cooling/Calibration - The FPA must be cooled and calibrated. The CLU’s IR detectors are cooled using a Dewar flask and a closed-cycle Stirling engine. But in the missile there is not sufficient. So prior to launch, a cooler mounted on the outside of the launch tube activates the electrical systems in the missile and supplies cold gas from a Joule-Thompson expander to the missile detector assembly while the missile is still in the launch tube. When the missile is fired this external connection is broken and coolant gas is supplied internally by an onboard argon gas bottle. The gas is held in a small bottle at high pressure enough coolant for the duration of the flight approximately 19 seconds.

The seeker is calibrated using a chopper wheel. This device is a fan having 6 blades: 5 black blades with very low IR emissivity and one semi-reflective blade. These blades spin in front of the seeker optics in a synchronized fashion such that the FPA is continually provided with points of reference in addition to viewing the scene. These reference points allow the FPA to reduce noise introduced by response variations in the detector elements.

3) Stabilization - The platform on which the seeker is mounted must be stabilized with respect to the motion of the missile body and the seeker must be moved to stay aligned with the target. The stabilization system must cope with rapid acceleration, up/down and lateral movements. This is done by a gimbal system, accelerometers, spinning mass gyros (or MEMS), and motors to drive changes in position of the platform. The system is basically an autopilot. Information from the gyros is fed to the guidance electronics which drive a torque motor attached to the seeker platform to keep the seeker aligned with the target. The wires that connect the seeker with the rest of the missile have no friction to keep the seeker platform balanced.

Tracker
The tracker is key to guidance/control for an eventual hit. The signals from each of the 4,096 detector elements in the seeker are passed to the FPA readout integrated circuits which reads then creates a video frame that is sent to the tracker system for processing. By comparing the individual frames the tracker determines the need to correct so as to keep the missile on target. The tracker must be able to determine which portion of the image represents the target. The target is initially defined by the gunner who places a configurable frame around it. The tracker then uses algorithms to compare that region of the frame based on image, geometric, and movement data to the new image frames being sent from the seeker, similar to pattern recognition algorithms. At the end of each frame the reference is updated. The tracker is able to keep track of the target even though the seeker’s point of view can change radically in the course of flight.

To guide the missile the tracker locates the target in the current frame and compares this position with the aim point. If this position is off center the tracker computes a correction and passes it to the guidance system which makes the appropriate adjustments to the four moveable tail fins, as well as six fixed wings at mid-body. This is an autopilot. To guide the missile the system has sensors that check that the fins are positioned as requested. If not, the deviation is sent back to the controller for further adjustment. This is a closed-loop controller.

There are three stages in the flight managed by the tracker: 1) an initial phase just after launch; 2) a mid-flight phase that lasts for most of the flight; and 3) a terminal phase in which the tracker selects the sweet spot for the point of impact. With guidance algorithms, the autopilot uses data from the seeker and tracker to determine when to transition the missile from one phase of flight to another. Depending on whether the missile is in top attack or direct attack mode, the profile of the flight can change significantly. The top attack mode requires the missile to climb sharply after launch and cruise at high altitude then dive on the top of the target (curveball). In direct attack mode (fastball), the missile cruises at a lower altitude directly at target. The exact flight path which takes into account the range to the target is calculated by the guidance unit.

Launch Tube Assembly
Both men carry a disposable tube called the Launch Tube Assembly which houses the missile and protects the missile from harsh environments. The tube also has built in electronics and a locking hinge system that makes attachment and detachment of the missile to and from the Command Launch Unit a very quick and simple process.

Command Launch Unit
The gunner carries a reusable Command Launch Unit (in addition to the Launch Tube Assembly) more commonly referred to as a CLU (pronounced "clue"). The CLU is the targeting component of the two part system. The CLU has three views which are used to find, target, and fire the missile. The CLU may also be used separately from the missile as a portable thermal sight. Infantry are no longer required to stay in constant contact with armored personal carriers and tanks with thermal sights. This makes the troops more flexible and able to perceive threats they would not otherwise be able to detect. In 2006 a contract was awarded to Toyon Research Corporation to begin development of an upgrade to the CLU enabling the transmission of target image and GPS location data to other units.

Advantages and disadvantages

Advantages
The portable system is easy to separate into main components and easy to set up when needed. Compared to more cumbersome anti-tank weapon systems, the difference is noticeable. For example, a TOW requires a heavy tripod stand, a bulky protective case for the thermal sight, a larger, longer launch tube, and requires much more time to assemble and prepare. The Javelin (although very heavy) is lighter than other missiles and their necessary parts.
Although the CLU's thermal imaging may hinder aiming, its thermal targeting allows the Javelin to be a fire-and-forget system. This gives the firer an opportunity to be out of sight and possibly moving to a new angle to fire from, or out of the area by the time the enemy realizes they are under attack. This is much safer than using a wire-guided system because the firer must stay at the same location the missile was fired from and guide the missile into the target.
Another advantage is the Javelin's power at impact. The missile has a tandem shaped charge in its warhead that is made to penetrate reactive armor. The Javelin was created with the intent to be able to penetrate any tank armor and was tested on the M1 Abrams Tank. With the top attack mode it has an even greater ability to destroy the tank because it can attack where most tanks are the weakest.

The soft launch capability of the Javelin allows it to have only a minimal backblast area. This enables the Javelin to be fired from inside a wide variety of structures. This gives the Javelin advantages in urban fighting over the widely used AT4, which has a very large backblast area, although this is lessened in the AT4 CS. A large backblast area would seriously injure personnel if fired from inside a small structure.

The missile also has a greater range than the system it replaces, the M47 Dragon

Disadvantages
The main drawback of the system is its 49.5 lb (22.5 kg) total weight. This does not account for the additional batteries (BA5590 lithium battery) which weigh around 2.25 lb (1.02 kg) each. Each battery is estimated to last 4 hours by the Javelin's manufacturer. A normal load for batteries (not counting the "just in case" extras that most teams carry) is 5–10. This number may be more or less depending on the length of mission. The system is designed to be portable by infantry on foot and weighs more than the original specified weight the army called for.
Another drawback of the system is the reliance on a thermal view to acquire targets. The thermal views are not able to operate until the refrigeration component has cooled the system. The manufacturer estimates 30 seconds until this is complete, but depending on the ambient temperature, this process may take much longer. The thermal view is occasionally hindered by a naturally occurring phenomena where the temperature of the earth heats or cools rapidly, and may interfere with the recognition and lock-on of the intended target.

M249 squad automatic weapon

The M249 squad automatic weapon (SAW), formally Squad Automatic Weapon, 5.56 mm, M249, is an American version of the Belgian Fabrique Nationale de Herstal (FN) Minimi. The M249 is manufactured in the United States and is used by all branches of the U.S. Armed Forces. The gun was introduced in 1984 after being judged the most effective weapon to address the lack of automatic firepower in small units. It was the only one of a number of candidate designs to pass tests set by the U.S. government. Tactically, it is employed at squad level and is operated by a single designated automatic rifleman. The gun provides the heavy volume of fire of a machine gun with accuracy approaching that of a rifle.

The M249 is gas-operated and air-cooled. It has a quick-change barrel so that the gunner can rapidly replace an overheated or jammed barrel. A folding bipod is attached near the front of the gun, though a heavy fixed tripod is also issued. It can fire both linked ammunition and ammunition kept in magazines.

M249 SAWs have been issued during every major United States conflict since the 1991 Gulf War. Soldiers are generally satisfied with the weapon's performance, though there have been many reports of clogging with dirt and sand. Due to the weight and age of the weapon, the U.S. Marine Corps (USMC) is considering designs for an infantry automatic rifle, which is planned to complement and partially replace the M249 in its service.

Development

In 1965, the U.S. Army's primary machine guns were the M2 Browning and M60. The M2 is a large-caliber heavy machine gun, usually mounted on vehicles or in prepared emplacements. The M60 was a more mobile medium machine gun intended to be carried with the troops to provide heavy automatic fire. Both are very heavy weapons and usually required a crew of at least two to operate efficiently, meaning they were best employed by platoons or larger sized units. The Browning automatic rifle, the army's main individual machine gun since its introduction in World War I, was phased out with the introduction of the M14 rifle, which has a fully automatic mode, in the 1950s. Until the introduction of the M249, "designated riflemen" in every squad had been ordered to use their weapons on the fully automatic setting. Because army doctrine usually required troops to use a rifle's semi-automatic mode on most occasions to increase accuracy and conserve ammunition, the M14 and M16 rifles used by the U.S. Army had not been designed with sustained automatic fire in mind, and overheated or jammed regularly. The 30-round magazines of these weapons also limited their sustained automatic effectiveness when compared with belt-fed weapons.

The Army decided that an individual machine gun, lighter than the M60 but with more firepower than the M16, would be advantageous; troops no longer would have to rely on rifles for automatic fire. Through the 1960s, the introduction of a machine gun into the infantry squad was examined in various studies. While there was a brief flirtation with the concept of a flechette- or dart-firing Universal Machine Gun during one study, most light machine gun experiments concentrated on the Stoner 63 light machine gun (LMG), a modular weapon which could be easily modified for different purposes. The Stoner 63 LMG saw combat for a brief period in Vietnam with the USMC, and later on a wider scale with the U.S. Navy SEALs.

In 1968, the Army Small Arms Program developed plans for a new 5.56 mm caliber LMG, though no funds were allocated (5.56 mm ammunition was viewed as underpowered by many in the armed forces). Studies of improved 5.56 mm ammunition, with better performance characteristics, began. The earliest reference to studies of other caliber cartridges for the LMG did not appear until 1969. In July 1970, the U.S. Army finally approved development of an LMG, with no specified calibre. At this time, the nomenclature "Squad Automatic Weapon" (SAW) was introduced. Actual design of alternative cartridges for the LMG did not begin until July 1971. A month later, Frankford Arsenal decided upon two designs for the new LMG: a 6 mm cartridge and a new 5.56 mm cartridge with a much larger case. Neither design was finalized by March 1972, when the Army published the specifications document for the planned SAW. The 6 mm cartridge design was eventually approved in May that year. Prior to July 1972, SAW development contracts were awarded to Maremont, Philco Ford, and the Rodman Laboratory at Rock Island Arsenal. These companies produced designs with Army designations XM233, XM234 and XM235 respectively—X denoting "experimental". Designs were required to have a weight of less than 9.07 kg (20 lb) including 200 rounds of ammunition, and a range of at least 800 meters (2,600 ft).

When the time came for developmental and operational testing of the SAW candidates, three 5.56 mm candidate weapons were included with the 6 mm candidates: the M16 HBAR, a heavy-barrel variant of the M16 designed for prolonged firing; the Fabrique Nationale de Herstal (FN) Minimi; and the HK 23A1. The initial round of tests ended in December 1974. In February 1976, the Minimi and Rodman XM235 SAW were selected for further development. At this time, opinions of the 6 mm cartridge were beginning to sour due to the logistical implications of providing yet another ammunition type to the infantry. In June, it was requested that the SAW specifications document be revised to emphasize standard 5.56 mm ammunition. In October, the requested revisions were approved, and bids were solicited for the conversion of the Rodman XM235 to 5.56 mm. Production of the converted XM235 was awarded to Ford Aerospace, and its designation was changed to XM248. A new M16 HBAR variant, the XM106, was developed in 1978, and soon after, Heckler & Koch lobbied to include a 5.56 mm conversion of its HK 21A1 (instead of the standard 7.62 mm NATO ammunition it was built for) in future SAW testing. The latter model was designated the XM262. At this time, the Minimi received the designation XM249. Testing of the four candidates resumed in April 1979.

In May 1980, the FN XM249 was selected as the best choice for future development on the grounds of performance and cost. The HK XM262 reportedly came a close second. In September, FN was awarded a "maturity phase" contract for further development of the XM249. Testing of the new XM249 began in June 1981. The official adoption took place on February 1, 1982.

The new gun entered U.S. Army service as the M249 squad automatic weapon in 1984, and was adopted by the U.S. Marine Corps a year later. The M249 model is built in the FN factory in Columbia, South Carolina and has a different butt from the regular Minimi.

Although found to be reliable and accurate, the M249 was considered to present unacceptable hazards in the form of an exposed hot barrel and sharp edges. There were also complaints that the front sight required special adjustment tools. On August 23, 1985, Undersecretary of the U.S. Army James R. Ambrose suspended M249 production pending the development of the product improvement program (PIP) intended to fix these problems. Congress deleted funds for the M249 from the Fiscal Year 1986 defense budget, then retroactively set aside the program's prior year's funds from the M249 program for other purposes, including retirement and pay raises. Over 1,100 M249s already issued were to remain in use, but be retrofitted with the PIP kit when it became available. Over 7,000 remaining M249s were to stay in storage at depots until corrective changes could be made. The PIP kit was eventually developed and implemented; production of the M249 soon resumed.

Design details
A U.S. Marine Corps M249 being fired from a tripod mount.

At 1,041 mm (41 in) long and 7.5 kg (17 lb) in weight (10 kg (22 lb) including a 200-round belt and plastic ammo box), the M249 is a large and heavy weapon. It fires from an open bolt and is gas operated. When the trigger is pulled, the bolt and bolt carrier move forward under the power of the recoil spring. A cartridge is stripped from the belt, chambered, and discharged, sending a bullet down the bore. Expanding propellant gases are diverted through a hole in the barrel into a chamber. This pressure moves a piston providing the energy to extract and eject the spent casing as well as advance the belt and compress the recoil spring, thus preparing for subsequent shots. When the operator releases the trigger, the bolt carrier is held to the rear. When the belt is exhausted, the bolt carrier comes to a rest on an empty chamber.

The barrel has a rifling twist rate of one turn in 180 mm (7 in). Because firing heats up the bore, the air-cooled barrel is equipped with a mechanism to remove and replace the barrel assembly with a spare. A folding bipod with adjustable legs is attached near the front of the weapon, though there are provisions for hard-mounting to a tripod or vehicle mount. The M249 provides accuracy approaching that of a rifle, combined with the sustained volume of fire of a machine gun. Its original gas regulator offered two different gas port sizes, allowing cyclic rates of fire of 750 rounds per minute (r/min) or 1,000 r/min. The latter setting was intended for adverse conditions such as an excessively dirty firearm or cold weather. The two-position gas regulator was discarded as part of a product improvement program. Sustained rate of fire, the rate of fire at which the gunner can fire continuously without overheating, is approximately 85 r/min.

The M249 fires the 5.56x45mm NATO cartridge, usually a combination of one M856 tracer and four M855 ball cartridges fed from M27 linked belts. Belts are typically held in a hard plastic or soft canvas box attached to the underside of the weapon.