Also known as Composition 4, C-4 plastic explosive packs quite a punch. Being the standard-issue demolitions charge for the Army before the war, it's still finding much use in the harsh environment of the Mojave Wasteland. A remotely detonated charge, it can be implemented in many ways for effect and entertainment. Like most explosives it can be reverse pickpocketed. The detonator is acquired separately. Unlike hand-held explosives like the frag grenade or dynamite, C-4 causes a huge explosion and should not be detonated until you have put a respectable distance between it and yourself.
Reverse pickpocketing plastic explosive will arm it. If you detonate it while hidden, and stay hidden, you will not be blamed for the crime. Even if the target is dead the C-4 will still be present on their corpse and can be detonated. In fact, reverse-pickpocketing isn't necessary; C-4 can also be easily planted nearby or on places where the intended victim frequently visits as part of their schedule, such as on beds or chairs. C-4 charges can be placed in plain view of anyone, as it is not a crime nor an aggressive action to deploy them. Therefore it is easy to set up ambushes with C-4, though its high cost is a deterrent. Non-player characters who see you placing it may make remarks such as "I can see what you're doing!" but they will take no other action. As long as you detonate it while hidden, you will not suffer any ill reputation effects. However, if the victim is hit when throwing down the charge or if the target wasn't successfully killed with the initial blast, they will become hostile to the player.
If multiple C-4 charges are dropped, they will all go off simultaneously when the detonator is activated.
It is possible to trigger a C-4 charge without a detonator by shooting it. As long as you remain hidden, non-player characters will not become hostile (a silenced weapon is useful in these cases).
As an improved holdout weapon, it can be brought into 'weapon free' areas such as casinos with a sneak skill of 50.
4 can be found inside Vault 19. One is hiding under the couch in the Northeast corner of the southwest room on the Living Quarters floor, which is in the in the Blue Quarters section. To get past the door, talk to Philip Lem and he will give you a pass key if you accept his quest. Another is in between the filing cabinets behind the desk in the Doctor's office. The third is between the two vending machines in the cafeteria, around the left side of the Nuka-Cola machine. The last C-4 is located just outside the locked underground entrance to the Overseer's office, between the door and the debris pile.
Can be bought from Lacey in the Mojave Outpost Barracks, about 8 explosives and 1-2 detonators.
2 total can be found in two floating, wooden Explosive crates on the east shore of the Colorado River near a small, unmarked cave with 4 lakelurks guarding 3 egg clutches. The small cave is south of the Hoover Dam. It is further south than the large cove just below the dam, round the next major bend in the river. One way to get there is to go north up the river from Cottonwood Cove. (It is also possible to travel Northeast of the Abandoned BoS Bunker, carefully climb down the cliff, and swim to the other side of the river. The lakelurks can attack from the bank while you're in the river so you may want to take care of them while on the cliff).
About 6 can be found in the top level of Silver Peak Mine in explosives crates, just outside the fence-door, behind which is a Remnants power armor helmet.
Dead Money 3 can be found with a detonator in the Sierra Madre. Enter the Police Station via the west doorway. Turn north at Dog's cell to enter a short hallway & face west. Enter the first door on your right. In this room in an Average locked locker leaning in the north west corner of the room.
Honest Hearts 1 can be found in Zion Canyon. It's located in Two Skies Cave adjacent to a reloading bench, and next to a computer terminal.
C-4 cannot be detonated remotely if you do not have a detonator. However, one can shoot or set off an explosion nearby it when it's placed on the ground to detonate it.
You can detonate from immense range. The max range is well over 200 meters or 14000 game units; however, actors won't render outside of 200m, making it pointless to detonate at this range. C4 should only be detonated when the target non-player character can be seen.