1-14. TECHNICAL PRINCIPLES OF OPERATION. The M203 grenade launcher is lightweight and compact and must be attached to M16 series rifles. The M203A1 grenade launcher is light-weight and compact and must be attached to M4 series carbines.
a. Open the launcher, insert a round, and close the launcher.
b. Place on SAFE.
c. Place the launcher to your shoulder. Keep muzzle pointed at target and move the safety from the SAFE to the FIRE position.
d. Align the front and rear of the quadrant sight assembly with the target and squeeze the trigger.
e. Squeezing the trigger releases the firing pin and allows it to impact the primer on the round.
f. The primer ignites the propellant in the round.
g. Gas from the burning propellant pushes the projectile along the barrel of the launcher.
h. The rifling in the barrel causes the projectile to rotate, which provides stability during flight to the target.
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