C4

C4, is an explosive featured in Call of Duty 4: Modern Warfare, and Modern Warfare 2.

Call of Duty 4
In multiplayer the C4 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 L1 (Left trigger on 360) you will throw the C4, which will stick to walls, cars, etc. Pressing R1 (Right trigger on 360) will then detonate the C4 (.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 C4 is not popular in multiplayer modes due to the necessary remote detonation of the C4 which proves troublesome for Snipers and is commonly used by those who wait for someone to walk into the C4 then detonate it. The claymore is preferred more by Sniper players who rely on actually sniping and have no time to detonate the C4 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. Another disadvantage of planting C4 at your flag in Domination is that the C4 can be seen beforehand by the enemy and detonated by gunfire. This can be avoided if the player camps in a hidden location to watch the flag, to know when to detonate the C4.

Tactics
The remote action of the C4 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 C4. However, the advantage of using C4 over a claymore is user safety; the C4 can be thrown quite a distance to a spot that could be very open and hazardous.

C4 can be used as a grenade instead of a mine. For example, C4 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.

C4 is used more often in objective-based modes like Search and Destroy, Sabotage, Headquarters. and Domination. When planting C4 at a point of interest, such as an objective, discretion is the key. Poorly-placed C4 acts only as a short deterrent. Superior placement for C4 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 C4 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.

In Domination, a good tactic is to throw C4 close to a flag, because the player will notice when an enemy is capturing it. It is best to try and hide it in scenery, or throw it into a dead body. this will make it less suspicious.

Single Player
The C4 is constantly seen in the campaign as the primary weapon to take out key objectives, where the player 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 the objective is to destroy the ZPU-4 in order for friendly helicopters to pass by. Also, the player will have to destroy an electrical tower with C4 in the level Ultimatum.

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, the throwing range of C4 is very low, 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, (Except on the PC Versions, where you must tap the "Use" key twice: "F" by default), which can be useful if you have a C4 out you need to detonate, but have C4 in inventory from Scavenger or One Man Army. In this case, pressing the equipment button will not detonate your C4, it will simply throw another C4.

Tactics

 * This is a very good equipment for defense on Search and Destroy and Demolition, especially for Snipers with excellent aim. One can quickly run up to the Bomb Site, plant a C4 and get to cover. When the attacker is planting the bomb, detonate it. This should kill the player, or at least wound them, making them easy to pick off.
 * The above tactic also works well on Domination, especially open ground command points where no obstacles are present to hide.
 * C4 can be placed in doorways often used by the enemy. When one or more enemies are walking through it, using it can be an easy way to rack up kills.
 * Danger Close works especially well as it increases the blast radius.
 * If Scavenger is equipped and another is picked up, you can simply shoot it, especially when using a Sniper Rifle or FAL with good range and zoom. This effectively turns it into a less reliable C4 detonated on the players command.
 * When defusing a bomb if you have a C4 planted, pressing the trigger will result in blowing up the C4 but you will still defuse the bomb. (Only tested in demolition).
 * In Domination when a enemy is capturing a command point the point will start blinking or the team announcer may alert players. Plant C4 at a command point and when you are alerted detonate the C4 to kill the enemy.
 * In Domination on Skidrow, there is some C4 on the wall at B. This is usually very good at hiding your own C4 as players are used to seeing C4 there.
 * You can plant it on a car, and wait there with a heartbeat sensor. When someone comes by the car, you can detonate it, getting a kill for a Humiliation challenge.
 * In Search and Destroy and Demolition use a Riot Shield, Danger Close, Scavenger and put the C4 on the bomb. Wait in a corner with the Riot Shield out for protection and detonate the C4 when a player gets close enough to it.

Trivia

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