C4

Composition 4, often shortened to "C-4", is a common variety of military plastic explosive.

The term composition is used for any stable or plastique explosive (stable meaning it is very difficult to detonate accidentally, unlike gunpowder or nitroglycerine), and "Composition A" and "Composition B" are other known variants. Composition-4 is 1.34 times as explosive as trinitrotoluene, which is more known as "TNT". It has gained public notoriety due to exposure in media including films and video games.

C-4 is made up of explosive, plastic binder, plasticizer and, usually, marker or taggant chemicals such as 2,3-dimethyl-2,3-dinitrobutane (DMDNB) to help detect the explosive and identify its source.

As with many plastic explosives, the explosive material in C-4 is RDX (cyclonite or cyclotrimethylene trinitramine) which makes up around 91% of the C-4 by weight. The plasticizer is diethylhexyl or dioctyl sebacate (5.3%) and the binder usually is polyisobutylene (2.1%). Another plasticizer used is dioctyl adipate (DOA). A small amount of SAE 10 non-detergent motor oil (1.6%) is also added.

C-4 detonates with a pressure wave of about 8,040 meters per second (26,400 ft/s) equaling 28,900 km/h (18,000 mph).

C-4 is manufactured by combining RDX slurry with binder dissolved in a solvent. The solvent is then evaporated and the mixture dried and filtered. The final material is an off-white solid with a feel similar to modeling clay.

Call of Duty 4
In multiplayer the C-4 is a first tier perk and you get two when it is used, it has a higher damage than the claymore and also has higher splash damage than the claymore. When the perk is used, press left on the D-Pad and your character will pull out a detonation trigger, then by pressing the Left trigger (L1 on PS3) you will throw the C-4, which will stick to walls, cars, etc. Pulling the Right trigger (R1 on PS3) will then detonate the C-4 (.83s delay). Alternatively, you can detonate it by double tapping the reload button (use button in PC version) with your main weapon out. Unfortunately the C-4 is not popular in multiplayer modes due to the necessary remote detonation of the C-4 which proves troublesome for Snipers and is commonly used by those who wait for someone to walk into the C-4 then detonate it. The claymore is preferred more by Sniper players who rely on actually sniping and have no time to detonate the C-4 as the claymore detonates when an enemy walks in front of it automatically. Most players use C4 in the Domination game mode and drop it at their flags. Since the game tells the player when they are losing a flag the C4 is then detonated. The disadvantage of this is that if the player dies, the C4 must be replanted.

Tactics
C-4 Mine: The remote action of the C-4 requires an ambush tactic when used as a mine. Specifically, the user must know by sight, sound, friendly intel, or objective notification when the enemy is close to the C-4. However, the advantage of using C-4 over a claymore is user safety; the C-4 can be thrown quite a distance to a spot that could be very open and hazardous.

C-4 Grenade: C-4 can be used as a grenade instead of a mine. For example, C-4 can be used when the user is out of grenades, when the enemy is in a difficult spot, or when grenade cooking is needed, but not possible. This technique can also be used in conjunction with Martyrdom as if the user dies while holding the C4, the C4 drops and becomes live. The grenade will go off, triggering the C4, which has a slightly larger blast than a grenade.

C-4 Planting: C-4 is used more often in objective-based modes like Search and Destroy, Sabotage, Headquarters. and Domination. When planting C-4 at a point of interest, such as an objective, discretion is the key. Poorly-placed C-4 acts only as a short deterrent. Superior placement for C-4 involves dark corners, deep grass, or inside movable items (crates, boxes, trash, etc.). More importantly, the 3-Dimensional properties of the blast can be taken advantage of by placing the charge on the ceiling or on the underside of over-hanging ledges.


 * In Search and Destroy, do note that the targets you are defending will be two crates on a single pallet, so will have a separation in the middle. Throw C-4 into this crevices, and detonate it remotely when the enemy is in the right position to be killed.


 * Some players enjoy 'suicide bombing' while using an SMG or the Sniper on the OpFor team, as it gives the player a shemagh (traditional head wrap which makes them 'look' like a suicide bomber as it hides everything but the eyes). They will equip Extreme Conditioning and Juggernaut so they can run up to the target, throw a C4 and detonate it quickly, usually killing them both. Although, not a very viable tactic, it is quite fun on Private Matches against other 'suicide bombers'


 * In Search and Destroy and Sabotage, when planting or defusing the bomb, if they hold the L1 button while arming/disarming the bomb, the player will throw a fake C4 that cannot be blown up, but if enemies see it, they may attempt to destroy it, wasting their time and possibly giving away their position. Observant players will know that it is fake because the red light in the center will not be blinking. Players with Bomb Squad will know that it is fake because the skull icon will not appear over it.


 * It is worth noting that most players will not be actively looking out for C4s, especially in non objective-based matches, as many players are accustomed to using Claymores (or having them used against them). Therefore, a C4 is far more likely to go unnoticed if it happens to be in plain sight. Additionally, C4s are overall less conspicuous, as they do not emit trip lasers, like a Claymore, and they are not as bright.

Single Player
The C4 is constantly seen in the campaign as the primary weapon to take out key objectives, where you would have to arm the explosive and travel to a safe distance before detonating the weapon. An example of this would be the level The Bog, where you have to destroy the ZPU-4 in order for friendly helicopters to pass by. Also, you have to destroy an electrical tower with C4 in the level Ultimatum. However you can still use it to kill enemies if you have some in your inventory.

Call of Duty: Modern Warfare 2
C4 returns in Call of Duty: Modern Warfare 2, this time in the equipment slot instead of via perk. Another change is characters are given only one C4, but it is arguably more powerful and has a bigger blast radius than in Call of Duty 4: Modern Warfare, but the throwing range is laughable, requiring deliberate placement rather than throwing. Also, because it is in the equipment slot, it can be placed with a single button. This is noticeably faster than Call of Duty 4's method, which required switching to C4 as a weapon via the directional pad and then throwing it. But detonating is slower, since there's an animation of pulling out the detonator and activating it, in contrast with having the detonator already equipped in Call of Duty 4. Single player retains the method of assigning C4 to a directional pad button. However, C4 will detonate instantly if reload is pressed twice, essentially negating such disadvantages.

As with the previous game it is useful to place it on objectives (I.E. Domination flags, Sabotage targets, etc.) and use it as a mine whenever an enemy nears it. It can be used as a rudimentary grenade, but can't be thrown as far and must be detonated by the player. However, unlike frag and semtex grenades, there is no warning indicator for a nearby C4 satchel, and C4 can be detonated in midair by pressing reload twice quickly.

C4 also makes a return in the single-player levels of Modern Warfare 2, but rarely in the character's inventory - it is given when you need it for an objective (Plant C4 on bodies, etc.)

C4 will detonate if you press reload twice very quickly, which can be useful if you have a C4 out you need to detonate, but have C4 in inventory from scavenger. In this case, pressing the equipment button will not detonate your C4, it will simply throw another one.

Trivia

 * The C4 makes an appearance in the extended level of F.N.G., where Sgt.Newcastle teaches you how to arm and detonate a C4 block. He tells you "Looks like my ex-wife was kind enough to donate her car to further your education Soap." Watch the video here.


 * In real life, C4 cannot be detonated by gunshot, as it is a plastic explosive. This is not the case in the game, for balance reasons.
 * When you have the deathstreak Martyrdom in Multiplayer, the grenade will not drop if you have C4 planted.
 * A common tactic with C4 is to "suicide bomb" enemy players by running at an enemy and detonating the C4.
 * In Modern Warfare 2, the only way to recover a C4 in multiplayer after placing (or detonating) is to use Scavenger perk and take ammo from a dead body; however, this is ill-advised because when taking C4 with Scavenger, you will pick up more C4 and instead of detonating, throw another C4 pack. This can be useful in some situations, but in panic moments where you are hoping to use C4 as a trap, this can be very frustrating. Remember, pressing reload twice detonates C4 instantly, so try not to rely on the much slower method of pressing the equipment button again. The player can also use One Man Army to "switch" to the same class, replenishing ammo and equipment.
 * In both Modern Warfare and Modern Warfare 2, C4 can be detonated by double-tapping the action button. This is useful when you have your weapon equipped, or have picked up another C4 pack using the Scavenger perk.
 * C4 in Modern Warfare 2 is white instead of the tan C4 that was in Modern Warfare.

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