This manual provides technical information, training techniques, and combat techniques of the M203 grenade launcher. Intended users include leaders and designated grenadiers, who will use this information to successfully integrate the M203 into their combat operations. This manual discusses gunnery training and train-the-trainer, and includes an appendix on the M79 40-mm grenade launcher. The tactical positions shown in this manual were drawn to enhance the reader’s understanding of related subject material and are not tactically correct. Trainers must ensure that safety procedures are observed at all times. Leaders, trainers, and soldiers must remember that safety is everyone’s responsibility. All training should be conducted as though the weapon is fully loaded. At no time while using this manual does speed or accuracy override the safety procedures.