There is little research on improved hand grenades, since these do exactly what is required. The Marines maintain a stock of more than 1,138,000 grenades of all types, showing how important they are to the firepower of the Corps.
M203 40mm Grenade Launcher
One of the problems with hand grenades is that a human being (even Dan Marino) can only throw one so far. In World War I grenade-throwing attachments were developed for bolt-action rifles to provide more standoff range for the infantry. These were not direct-fire weapons, and they were not terribly accurate; the grenades had to be lofted, like a mortar round. During the Vietnam War the U.S. Army introduced the M79 grenade launcher (nicknamed the "thump gun"). This stubby weapon, resembling an oversized, sawed-off shotgun, fired a 40mm shell, called a grenade, to a range of about 150 meters/492 feet. At this range, a good thump gunner could put a round through a door or window. Each 40mm projectile has about the same lethality as a hand grenade, but with considerably more accuracy and range. There are several different types (smoke, fragmentation, gas, flechette, etc.), with various effects.
The M79 was used extensively in Vietnam, and is still favored by law enforcement agencies for riot control and SWAT teams, but it is an extra weapon the soldier has to lug around that is not useful for anything else. Thus, the M203 grenade launcher was created. The M203 is a "clip-on" device, which attaches to the bottom of the forward receiver of an M16A2 combat rifle. A Marine with the M203 still has full use of his M16A2, but he can also launch 40mm grenades. You load it by pushing the barrel of the M203 forward, and then sliding a round into the breech. By pulling the barrel tube backwards, you lock the weapon shut and are ready to fire. All you have to do is release the safety, aim the weapon, and pull the M203's trigger, located just forward of the magazine loading chute of the M16A2. Surprisingly, the M203 is quite accurate, and gunners can put rounds through a door or window at quite a good range. Each fire team includes one M203 gunner. It is a deadly little weapon, well liked by Marines.
Mines
Mines are weapons that wait, sometimes for decades. Combat soldiers both love and hate land mines. They love to sit behind a minefield and watch the enemy blunder into it. But they hate the feeling of helplessness and terror that comes from being caught in a minefield, seeing their friends suddenly and horribly maimed. And then once the war is over, the winners get to pick all the damned things up and disarm them. Unfortunately, this doesn't always happen, and large areas of luckless countries like Cambodia, Angola, and Afghanistan have been rendered uninhabitable by millions of land mines. Although some European countries that profited hugely from the sale of land mines are beginning to ban their export for humanitarian reasons, mines are so effective and cheap that there is little hope of a workable international law prohibiting their manufacture and use.
The Marines deploy a variety of different mines, including the following, which are man-portable:
• M16A1 "Bouncing Betty" — This is a "bounding" anti-personnel mine. When someone steps on one of the firing prongs (which are left exposed when the M16A 1 is buried), a small propelling charge fires it about 6f/1.8m into the air, at which point it detonates. The M16A1 contains a 1-1b/ .45-kg explosive charge, which produces a lethal fragmentation range of around 88f/27m.
• M18A1 "Claymore" — This is a flat curved plate filled with steel balls embedded in plastic explosive. It has folding metal prongs that stick into the ground and a chilling label embossed on the housing: "This side toward enemy." It functions like a huge shotgun shell. Once the M 18A1 is emplaced, it can either be fired by a trip wire or command-detonated from a distance. When detonated, the 1.5-1b/.68-kg C-4 charge fires a 60deg fan-shaped pattern of fragments, each the size of a ball bearing. The fragments are lethal out to a range of around 328f/100m. The Claymore is primarily used for ambushes, but it can also function as a "silent sentry," covering ground that cannot be brought under direct observation and fire.
Anti-personnel mines are effective against opposing infantry, and Marines can carry them in sufficient numbers to make them a real threat. Though there are larger mines like the M15 and M18 used against tanks, they are too heavy to be man-portable.
Explosives and Breaching Tools
In addition to grenades and mines, Marines frequently carry supplies of plastic explosives and detonation gear for demolitions. They may use explosives to breach doors and other obstacles. In most cases, these are improvised devices, tailored to a particular situation. Today, C-4 is the most common explosive used by U.S. forces. With the consistency of modeling clay, it is extremely powerful, clean, and quick-burning. Another common explosive tool is detonator cord, which burns so hot and fast it can cut through metal. These explosives are usually detonated electrically, with a positive control whenever possible. Explosives experts hate time fuses, because they are just one more thing to fail, or to be disarmed later.
The growing menace of domestic terrorism raises legitimate concerns about showing people how to build homemade explosive devices. For that reason I will not give you specifics. That said, explosives have some positive uses; they are not always used to kill or injure people. Consider a door. Any cop will tell you that going though a door with a perpetrator on the other side is a good time to have your insurance policy paid up and your sins confessed. Door-busting quickly and safely is vital, especially in the tricky business of hostage rescue. So consider this little improvised device.
Cut a large coffee tin or other institutional food container in half, down the long axis. You now have a concave container, into which you loop a length of detonator cord and a detonator. On top of the detonator cord, you pack the remaining space with soft plastic packages of saline solution from the medical supplies carried by your Navy corpsman. Once this is done, the open side is sealed with duct tape. Now apply double-sided sticky foam tape over the duct tape. Then slap the sticky side onto the door you want to go through and step back. When the detonator is fired, it drives the saline liquid forward with such force that the door is knocked off its hinges. Since the explosion is quick and clean, and the area is drenched with the saline solution (its just salt water, remember), there is virtually no danger of fire.
Marines learn dozens of such tricks for taking down different kinds of structures. To a properly trained Marine, explosives are another tool, like a saw or bulldozer, to get a job done. In the arts of combat, Marines are world-class masters of creative improvisation.
Tools of the Trade
"We must not be lulled into complacency because we have always been ready, relevant, and capable. What might be ready, relevant, and capable today may be less so the day after tomorrow. We must anticipate change, adapt to it, and foster it. We shall remain relevant only if we are willing to meet future challenges and adapt to new needs."