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 rifle barrel stop 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 4-14) 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 stop and the five-position shim plate.

The following steps describe checking for sliding motion with the next or #2 notch up, and against the rifle barrel stop. 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.


Endurance testing indicated that it may be necessary to switch to another shim plate 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 re-mounted to the rifle.

1. Follow the steps as described in para a. Installation to attach the quick release bracket (1) to the M203A2.

2. Compare the illustration below with the quick release bracket for the purpose of

2. Compare the illustration below with the quick release bracket for the purpose of

M203a2 Quick Release Bracket

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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