Here are a couple of images of Trumpeter's 1/3 scale AR15/M16/M4 Family M16A2/M203 Rifle with Grenade Launcher and Trumpeter's 1/3 scale AR15/Mi6/M4 Family M16A1 Rifle.
The M16 (more formally Rifle, Caliber 5.56 mm, M16) is the United States military designation for the AR-15 rifle. Colt purchased the rights to the AR-15 from ArmaLite and currently uses that designation only for semi-automatic versions of the rifle. The M16 rifle fires the 5.56x45mm cartridge and can produce massive wounding effects when the bullet impacts at high velocity and yaws in tissue leading to fragmentation and rapid transfer of energy.
The M16 entered United States Army service and was deployed for jungle warfare operations in South Vietnam in 1963, becoming the standard U.S. rifle of the Vietnam War by 1969, replacing the M14 rifle in that role. The U.S. Army retained the M14 in CONUS, Europe, and South Korea until 1970. Since the Vietnam War, the M16 rifle family has been the primary infantry rifle of the U.S. military. With its variants (M16A1, M16A2, M16A3, and M16A4), it has been used by almost a hundred countries. Total worldwide production of M16-style weapons since the design's inception has been approximately 8 million, making it the most produced firearm in its caliber. The M16 is being phased out in the United States Army and is being replaced by the M4 carbine series as of 2010.
XM16E1 and M16A1 (Colt Model 603)
The U.S. Army XM16E1 was essentially the same weapon as the M16 with the addition of a forward assist and corresponding notches in the bolt carrier. The M16A1 was the finalized production model in 1967. To address issues raised by the XM16E1's testing cycle, a closed, bird-cage flash suppressor replaced the XM16E1's three-pronged flash suppressor which caught on twigs and leaves. Various other changes were made after numerous problems in the field. Cleaning kits were developed and issued while barrels with chrome-plated chambers and later fully-lined bores were introduced.With these and other changes, the malfunction rate slowly declined and new soldiers were generally unfamiliar with early problems. A rib was built into the side of the receiver on the XM16E1 to help prevent accidentally pressing the magazine release button while closing the ejection port cover. This rib was later extended on production M16A1s to help in preventing the magazine release from inadvertently being pressed. The hole in the bolt that accepts the cam pin was crimped inward on one side, in such a way that the cam pin may not be inserted with the bolt installed backwards, which would cause failures to eject until corrected. The M16A1 remains in service in limited numbers in the United States but is still standard issue in many world armies.
The development of the M16A2 rifle was originally requested by the United States Marine Corps as a result of the USMC's combat experience in Vietnam with the XM16E1 and M16A1. The Marines were the first branch of the U.S. Armed Forces to adopt the M16A2 in the early/mid 1980s with the United States Army following suit in the late 1980s. This rifle is now the current issue to Marine Corps' recruits in both MCRD San Diego and MCRD Parris Island. Modifications to the M16A2 were extensive. In addition to the new rifling, the barrel was made with a greater thickness in front of the front sight post to resist bending in the field and to allow a longer period of sustained fire without overheating. The rest of the barrel was maintained at the original thickness to enable the M203 grenade launcher to be attached. The front sight was now a square post with 4 detent positions, adjustable for vertical zeroing by using a cartridge, nail or special tool. A new adjustable rear sight was added, allowing the rear sight to be dialed in for specific range settings between 300 and 800 meters to take full advantage of the ballistic characteristics of the new SS109 rounds and to allow windage adjustments without the need of a tool or cartridge. The flash suppressor was again modified, this time to be closed on the bottom so it would not kick up dirt or snow when being fired from the prone position, and acting as a recoil compensator. The front grip was modified from the original triangular shape to a round one, which better fitted smaller hands and could be fitted to older models of the M16. The new handguards were also symmetrical so that armories need not separate left and right spares. The handguard retention ring was tapered to make it easier to install and uninstall the handguards. A notch for the middle finger was added to the pistol grip, as well as more texture to enhance the grip. The buttstock was lengthened by 5/8 inch (16 mm). The new buttstock became ten times stronger than the original due to advances in polymer technology since the early 1960s. Original M16 stocks were made from fiberglass-impregnated resin; the newer stocks were engineered from DuPont Zytel glass-filled thermoset polymers. The new stock included a fully textured polymer buttplate for better grip on the shoulder, and retained a panel for accessing a small compartment inside the stock, often used for storing a basic cleaning kit. The heavier bullet reduces muzzle velocity from 3,200 feet per second (980 m/s), to about 3,050 feet per second (930 m/s). The A2 also uses a faster twist rifling to allow the use of a trajectory-matched tracer round. A spent case deflector was incorporated into the upper receiver immediately behind the ejection port to prevent cases from striking left-handed users.
The action was also modified, replacing the fully-automatic setting with a three-round burst setting. When using a fully-automatic weapon, poorly trained troops often hold down the trigger and "spray" when under fire. The U.S. Army concluded that three-shot groups provide an optimum combination of ammunition conservation, accuracy and firepower. There are mechanical flaws in the M16A2 burst mechanism. The trigger group does not reset when the trigger is released. If the user releases the trigger between the second and third round of the burst, for example, the next trigger pull would only result in a single shot. Even in semi-automatic mode, the trigger group mechanism affects weapon handling. With each round fired, the trigger group cycles through one of the three stages of the burst mechanism. Worse, the trigger pull at each of these stages may vary as much as 6 lbf (27 N) in pressure differential, detracting from accuracy.
All together, the M16A2's new features added weight and complexity to the M16 series. Critics also point out that neither of the rear sight apertures is ideally sized. The smaller aperture was described as being too small, making quick acquisition of the front sight post difficult; and the larger aperture was described as being too large, resulting in decreased accuracy. To make matters worse, the rear sight apertures are not machined to be on the same plane. In other words, the point of impact changes when the user changes from one aperture to the other. The rear sight's range adjustment feature is rarely used in combat as soldiers tend to leave the rear sight on its lowest range setting of 300 meters. This distance is seen by many as an excessively long range for the minimum setting, given that most engagements take place at significantly shorter ranges. Despite criticism, a new rifle was needed both to comply with NATO standardization of the SS109 (M855) and to replace aging Vietnam era weapons in the inventory.
The M203 is a single shot 40 mm grenade launcher designed to attach to a rifle. It uses the same rounds as the older M79 "shotgun"-type grenade launcher, which utilize High-Low Propulsion System to keep recoil forces low. Though versatile, and compatible with many rifle models, the M203 was originally designed for the U.S. M16 and its variant, the M4 Carbine. 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 of the M203 exist, as do versions designed specifically for many other rifles. The device attaches under the barrel, the launcher trigger being in the rear of the launcher, 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.