Principle Of The Fiveposition Shim Plate

The basic overall length between the barrel nut roll pin at the rear of the receiver, and the starting position shim plate cutout surface at the front, is approximately 11 inches. As noted in step 5, some sliding motion may be detectable between the carbine barrel shoulder and the front of the five-position shim plate at the starting, or minimum, overall length cutout position.

Subsequent re-insertion of the five-position shim plate to its #2, #3, #4, or maximum (fifth) length position (refer to step 2, page 4-10) will slightly increase the overall length of the assembly beyond the basic 11 inches, and therefore tend to minimize or eliminate any sliding motion between the barrel shoulder and the five-position shim plate.

At some point, the unit armorer will note that the shim plate will not fit into the cutout of the carbine barrel shoulder (as indicated as INCORRECT in step 5). At this point, go back to the next lowest position and secure, close, and lock the bracket around the carbine.

The following steps describe checking for sliding motion with the next or #2 notch up, and against the carbine barrel shoulder. If the #2 position does not minimize the sliding motion, repeat the procedure with the #3 notch up and so on. If the fifth or maximum position is desired, note that the "back" or smooth face of the shim plate is oriented towards the muzzle. Do not be concerned if only a small amount of sliding motion is still detectable with the shim plate in its apparently optimum setting, because the latch arm will compensate for this when it is closed and locked.

Quick Release Principle

ARMY TM 9-1010-221-23&P AIR FORCE TO 11W3-9-4-2 MARINE CORPS TM 07700A-23&P/2 NAVY SW 370-AE-MMI-010

1. Follow the steps as described in para a. Installation to attach the quick release bracket to the M203.

2. Compare the illustration below with the quick release bracket (1) for the purpose of familiarization with all positions of the five-position shim plate (2):

2. Compare the illustration below with the quick release bracket (1) for the purpose of familiarization with all positions of the five-position shim plate (2):

M203 Quick Release

3. Set the five-position shim plate in the bracket to the minimum position as illustrated, with the 2 dots down and facing the muzzle.

LEFT SIDE FRONT

VIEW VIEW

LEFT SIDE FRONT

VIEW VIEW

Quick Release Shim Plate
ARMY TM 9-1010-221-23&P AIR FORCE TO 11W3-9-4-2 MARINE CORPS TM 07700A-23&P/2 NAVY SW 370-AE-MMI-010

2-17. MAINTENANCE OF QUICK RELEASE BRACKET (CONT).

e. MOUNTING TO THE M4 CARBINE (CONT)

4. If present, remove the lower rail of the M4 adapter rail system from the M4 carbine. Move the rear of the M203A2 receiver into position around the carbine barrel. Confirm that the latch arm (3) of the bracket is fully open. Rotate the muzzle end of the M203A2 towards the carbine barrel while sliding the M203A2 firmly to the rear. Confirm that the roll pin in the rear of the M203A2 receiver engages the carbine barrel nut at the six o'clock position notch.

Colt M203a2

5. Firmly hold the M203A2 in position/back against the barrel nut of the carbine, while also holding the muzzle end of the M203A2 against the carbine's barrel. Inspect the five-position shim plate, looking from the top of the carbine barrel, and also from the front, as illustrated below. The inner notch of the shim plate should rest behind the shoulder of the barrel. Now, try to slide the M203A2 back and forth if possible, and note the distance of any sliding motion. Some motion will be detectable with most carbine barrels with the shim plate in its starting position. If during this step the cutout in the shim plate does not fit behind the barrel shoulder, it is most probably inserted at its maximum thickness (no dots facing the muzzle), or position #2, #3, or #4 (refer to step 2 on page 4-10).

NOTE

Endurance testing indicated that it may be necessary to switch to another shim plate (2) position after several thousand rounds have been fired. The unit armorer should check for excessive sliding motion each time the shim plate is removed for cleaning/lubrication and the M203A2 remounted to the carbine.

BARREL SHOULDER

BARREL SHOULDER

203 Cutouts

BARREL DIAMETER REAR OF SHOULDER

CORRECT

BARREL SHOULDER FITS INTO CUTOUT IN SHIM

INCORRECT

BARREL SHOULDER DOES NOT FIT INTO CUTOUT IN SHIM PLATE

PLATE

BARREL DIAMETER REAR OF SHOULDER

CORRECT

BARREL SHOULDER FITS INTO CUTOUT IN SHIM

INCORRECT

BARREL SHOULDER DOES NOT FIT INTO CUTOUT IN SHIM PLATE

PLATE

ARMY TM 9-1010-221-23&P AIR FORCE TO 11W3-9-4-2 MARINE CORPS TM 07700A-23&P/2 NAVY SW 370-AE-MMI-010

6. Remove the M203A2 from the carbine. Depress the plunger (4), withdraw the shim plate and re-insert it in the #2 position (refer to step 2, page 4-10). Note that the #2 position is indicated by a single dot stamped on its shim plate cutout, and that this side of the shim plate faces the muzzle.

7. Re-mount the M203A2 to the carbine's barrel nut and barrel shoulder. Attempt to slide the M203A2 from front to rear.

8. If forward and back motion is detected, repeat step 7 with the shim plate in the #3 position. If the assembly is now too long (it will not engage behind the barrel shoulder, but rides up onto the barrel's major diameter), go back to the last position tried with the shim plate, and complete the M203A2 attachment.

When the optimum position of the shim plate is established:

a. If necessary, hold the retaining spring out of the way and depress the plunger (4) to unlock the latch lever (5).

b. Rotate the latch arm (3) over the carbine barrel.

c. Catch the hook (6) in the hole of the latch arm.

d. Rotate the latch lever (5) down.

e. Depress the plunger (4). Make sure the retaining spring does not engage the plunger during this step.

f. Squeeze the latch lever fully closed (which allows the plunger to be released and snap forward). This will hold the latch lever in the fully closed/locked position.

NOTE

In its final motion, the latch lever may require very firm pressure against the bracket to allow the plunger to snap back into place, locking the latch lever closed. If necessary, use the buddy system. DO NOT use a vise or other mechanical device. Doing so may cause damage to the quick release bracket.

g. Rotate the M203A2 trigger guard (7) to engage the lip of the magazine well.

M203a2 Airsoft

ARMY TM 9-1010-221-23&P AIR FORCE TO 11W3-9-4-2 MARINE CORPS TM 07700A-23&P/2 NAVY SW 370-AE-MMI-010

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  • daniel
    How to install m203a2?
    8 years ago

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