This website is not affiliated with the U.S. government or military.

071-311-2125 (SL1) - Maintain an M203 Grenade Launcher

Standards: Cleared the M203 grenade launcher; disassembled the M203; cleaned and lubricated the M203; inspected the M203 before assembly; assembled the M203; and performed a function check on the M203.

Conditions: Given an M203 grenade launcher; cleaner, lubricant, preservative (CLP); thong; bore brush; and clean rags.

Standards: Cleared the M203 grenade launcher; disassembled the M203; cleaned and lubricated the M203; inspected the M203 before assembly; assembled the M203; and performed a function check on the M203.

Performance Steps

1.   Clear the M203 grenade launcher.

2.   Disassemble the M203 (figure 071-311-2125-1).

Figure 071-311-2125-1. Components of the M203 grenade launcher


WARNING: Before disassembling the weapon, clear the rifle and grenade launcher.

a. Remove the quadrant sight (if used) by loosening the knurled screw on the right side (figure 071-311-2125-2).

Figure 071-311-2125-2. Removing quadrant sight


b. Pull back the slip ring.  Lift up on the handguard and pull it to the rear to remove (figure 071-311-2125-3).

Figure 071-311-2125-3. Removing handguard


c. Press the barrel latch and move the barrel forward to the barrel stop (figure 071-311-2125-4).

Figure 071-311-2125-4. Unlocking and opening the M203 barrel


d. Press the barrel stop to release the barrel from the receiver and remove the barrel (figure 071-311-2125-5).

Figure 071-311-2125-5. Removing the M203 barrel

Note.  Further disassembly may be performed only by the armorer.

3.   Clean and lubricate the M203.

a. Bore.  Attach a clean, dry rag to the thong and thoroughly moisten the rag with CLP.  Pull the rag through the bore several times.  Attach the bore brush to the thong, pull it through the bore several times, and follow this with more rags, moistened with CLP, if needed (figure 071-311-2125-6).  Pull dry rags through the bore and inspect each rag as it is removed.  The bore is clean when a dry rag is removed unfouled. Pull a rag lightly moistened with CLP through the bore to leave a light coat of lubricant inside the barrel.

Figure 071-311-2125-6. Cleaning the M203 barrel


b. Breech insert.  Clean the face of the breech insert retainer with a patch and CLP.  Remove the CLP cleaner with dry rags, then lubricate the breech with a light coat of CLP.

c. All other parts.  Use a brush and dry rags to clean all other parts and surfaces.  Apply a light coat of CLP to the exterior of the launcher after cleaning.

d. Safety mechanism.  Clean the safety mechanism properly with CLP.  Lubricate the safety with CLP.

Note.  For cleaning the rifle portion of the launcher, refer to Task 071-311-2025.

4.   Inspect the M203 before assembly.

a. Check handguard for cracks, dents, or distortion that prevent its firm attachment to the rifle.

b. Check leaf sight for bent or damaged parts and for rust or corrosion.

c. Check leaf sight for legibility of marking.

d. Check barrel for cracks and general condition.  Inspect all parts for wear and damage.

e. Check for burrs, scratches, nicks, or other damage.

5.   Assemble the M203.

a. Press the barrel stop.  Slide the barrel into the receiver (figure 071-311-2125-7).

Figure 071-311-2125-7. Installing the M203 barrel


b. Move the barrel rearward to lock (figure 071-311-2125-8).

Figure 071-311-2125-8. Locking the M203 barrel


c. Install the handguard and secure with the slip ring (figure 071-311-2125-9).

Figure 071-311-2125-9. Installing the handguard


d. Install the quadrant sight (figure 071-311-2125-10).

Figure 071-311-2125-10. Installing the quadrant sight

6.   Perform a function check on the M203.

a. Check the proper operation of the sears.  Cock the launcher and pull the trigger.  The firing pin should release.  Hold the trigger to the rear and cock the launcher.  Release the trigger, then pull.  The firing pin should release.

b. Check the safety in both SAFE and FIRE positions with trigger.  Launcher must be cocked before safety can be placed in SAFE position.

c. Check the leaf sight windage adjustment screw for proper operation.  Do not move the elevation adjustment screw if the weapon has been zeroed.

d. Move barrel forward and back to be sure the stop and barrel latch function.

Evaluation Preparation: 

Setup:  At the test site, provide all materials and equipment given in the task conditions.

Brief Soldier: Tell the soldier he will perform unit maintenance on the M203 grenade launcher.

Performance Measures



1.   Cleared the M203 grenade launcher.



2.   Disassembled the M203.



a. Removed the quadrant sight.



b. Pulled back the slip ring.



c. Moved the barrel forward to the barrel stop.



d. Removed the barrel.



3.   Cleaned and lubricated the M203.



a. Cleaned the bore.



b. Cleaned the breech insert.



c. Cleaned all other parts.



d. Cleaned the safety mechanism.



4.   Inspected the M203 before assembly.



a. Checked the handguard.



b. Checked the leaf sight.



c. Checked the barrel.



d. Checked for burrs, scratches, and other damage.



5.   Assembled the M203.



a. Slid the barrel into the receiver.



b. Closed the barrel.



c. Installed the handguard.



d. Installed the quadrant sight.



6.   Performed a function check on the M203.



a. Checked operation of the sears.



b. Checked safety in both the SAFE and the FIRE positions.



c. Checked the leaf sight windage adjustment screws for proper operation.



d. Checked the barrel latch and the stop function.



Evaluation Guidance:  Score the soldier GO if all performance measures are passed. Score the soldier NO GO if any performance measure is failed. If the soldier scores NO GO, show him what was done wrong and how to do it correctly.







FM 23-31



TM 9-1010-221-10