Both the M203 dual-purpose weapon and the MK 19 grenade machine gun fire 40-mm high-explosive (HE) and high-explosive dual-purpose (HEDP) ammunition. Ammunition for these weapons is not interchangeable, but the grenade and fuze assembly hitting the target is identical. Both weapons provide point and area destructive fires as well as suppression. The MK 19 has a much higher rate of fire and a longer range; the M203 is much lighter and more maneuverable.
The grenadier is equipped with an M203 weapon system consisting of an M16 rifle and an attached 40-mm grenade launcher. The M203 allows him to fire high explosive rounds to suppress and destroy enemy infantry and lightly armored vehicles. He also can employ smoke to screen and cover his squad's movement, fire, and maneuver. During night and adverse weather conditions, the grenadier also may employ illumination rounds to increase his squad's visibility and mark enemy or friendly positions. The grenadier provides the fire team with an indirect fire capability out to 350 meters.
To reach combat readiness, the grenadier should consider his position, the capabilities of his weapon, and the combat conditions. Enemy personnel are seldom visible except when assaulting. Most combat fire must be directed at an area where the enemy has been detected or is suspected but cannot be seen. Area targets consist of objects or outlines of men irregularly spaced along covered and concealed areas (ground folds, hedges, borders of woods). Most combat targets can be detected by smoke, flash, dust, noise, or movement and are visible only for a moment. Some combat targets can be engaged by using reference points, predetermined fire, or range card data.
The nature of the target and irregularities of terrain and vegetation may require a grenadier to use a variety of positions to place effective fire on the target. In a defensive situation, the grenadier usually fires from a supported fighting position. Most combat targets have a low-contrast outline and are obscured. Therefore, choosing an aiming point in elevation is difficult.
The main consideration affecting the employment of 40-mm grenades within urban areas is the typically short engagement range. The 40-mm grenade has a minimum arming range of 14 to 28 meters. If the round strikes an object before it is armed, it will not detonate. Both the HE and HEDP rounds have 5-meter burst radii against exposed troops, which means the minimum safe firing range for combat is 31 meters. The 40-mm grenades can be used to suppress the enemy in a building, or inflict casualties by firing through apertures or windows. The MK 19 can use its high rate of fire to concentrate rounds against light structures. This concentrated fire can create extensive damage. The 40-mm HEDP round can penetrate the armor on the flank, rear, and top of Soviet-made BMPs and BTRs. Troops can use the M203 from upper stories to deliver accurate fire against the top decks of armored vehicles. Multiple hits are normally required to achieve a kill.
The 40-mm HEDP grenade has a small shaped charge that penetrates better than the HE round. It also has a thin wire wrapping that bursts into a dense fragmentation pattern, creating casualties out to 5 meters. Because they explode on contact, 40-mm rounds achieve the same penetration regardless of range.
If projected into an interior room, the 40-mm HEDP can penetrate all interior partition-type walls. It splinters plywood and plaster walls, making a hole large enough to fire a rifle through. It is better to have HEDP rounds pass into a room and explode on a far wall, even though much of the round's energy is wasted penetrating the back wall. The fragmentation produced in the room causes more casualties than the HE jet formed by the shaped charge.
The fragments from the HEDP round do not reliably penetrate interior walls. Office furniture sandbags, helmets, and protective vests (flak jackets) also stop them. The M203 dual-purpose weapon has the inherent accuracy to place grenades into windows at 125 meters and bunker apertures at 50 meters. These ranges are significantly reduced as the angle of obliquity increases. Combat experience shows that M203 gunners cannot consistently hit windows at 50 meters when forced to aim and fire quickly.
The M203 cannot reasonably deliver the rounds needed to breach a typical exterior wall. The MK 19 can concentrate its fire and achieve wall penetration. Firing from a tripod, using a locked down traversing and elevating mechanism is best for this role. Brick, cinder block, and concrete can be breached using the MK 19 individual HEDP rounds, which can penetrate 6 to 8 inches of brick. The only material that has proven resistant to concentrated 40-mm fire is dense stone such as that used in some European building construction. No precise data exist as to the number of rounds required to produce loopholes or breach holes with the MK 19; however, the rounds' explosive effects are dramatic and should exceed the performance of the caliber .50 machine gun.
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