m-4a1 m203 assualt rifle
Marines train with the M4 and M203 because it’s the easiest way to teach newbies how to shoot and how to throw a grenade, and how to survive both.
The M203 is the only thing that makes new marines cry, and maybe the grenade.
Marines train with M4 and M203, it’s like math class but with explosions.
Training with the M203 is like learning to ride a bike, but with a grenade launcher.