The coring charge is the first secondary weapon the player will get in the game, during the first level "Hero Training." The coring charge is your typical grenade. You throw it, and it explodes. The coring charge will explode on contact with any bot (Mil, Droid, etc.) if it doesn't hit the ground or a wall first. If the coring charge makes contact with the ground, or any of the environment first, it will retain its normal timer until detonation rather than exploding on contact. However, this mechanic does not apply to the slingshot. If a coring charge is launched by the slingshot, it will travel at a faster speed than being thrown normally, and explode on contact with anything. It is a small yellow stick of dynamite essentially. It was used originally to clear rocks and other debris in the mines, but was later used as a front-line explosive in the war against the Mils.
In-game description: "These standard yield explosive mining charges can obliterate a Mil into metal chum."