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SOUM: M16/M4.

The Department of Defense reported finding a small number of M16/M4 weapons that potentially could have an unintended discharge while manipulating the selector. TACOM (U.S. Army Tank-automotive & Armaments Command) issued a Safety Of Use Message (SOUM #18-004) about unintended discharges on M4A1s that had been through the Product Improvement Program, occurring after the operator pulled the trigger with the selector switch between the Semi and Auto detents. The weapon did not fire when the operator pulled the trigger and instead fired when the selector was moved further. The problem has been thought to be due to a "stack up" of differing tolerances from new parts.

This potential mechanical problem is uncommon. The Army converted 259,000 M4s to M4A1s in the past three years and initially found 881 with this problem and more found later. TACOM released an updated Function Check (SOUM #18-005) that easily determines if a M16/M4 (or AR-15) exhibits this problem. Ensure the weapon is unloaded and perform a Function Check: Pull the trigger while on Safe (nothing should happen), rotate to Semi and pull the trigger (hammer should fall), hold the trigger down while racking the charging handle (hammer remains cocked) and then release and pull the trigger (hammer should fall.) For military weapons, rotate to Auto or Burst and check the full auto or three-round burst as usual.

If that passes, continue by moving the selector lever to the Semi position, then move the selector between detents (such as Semi and Auto) and pull the trigger. The hammer should drop when the trigger is pulled and the selector is off Safe. If the hammer drops, repeat by re-cocking the hammer and slightly repositioning selector between settings again. If hammer doesn't drop, move the selector in either direction. It should not drop.

These additional steps will determine if a particular firearm is affected. If the Function Check is passed, there is no need to change Immediate Action. The old Department of Army Immediate Action procedure ("SPORTS") was replaced in 2016 with an improved procedure described in Training Circular 3-22.9, which is a very good training manual, can be distributed without restriction, and is available for free download. References still using SPORTS or other variations are out of date.

An Immediate Action amendment is unnecessary if the Function Check passed. Confirming correct mechanical function is an administrative action. SPORTS was replaced as a less effective approach than the new Immediate Action procedure in TC 3-22.9. Taking a tangled "immediate" six-step procedure and adding another step defies the point of immediate action. This low percentage mechanical problem only occurs while manipulating the selector. Immediate Action is only necessary after attempting to engage targets, meaning the weapon was already set to discharge and there is no need to manipulate the selector while performing it.

Fast X,

John M. Buol Jr.

AmericanGunsmith.info

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Title Annotation:THE EDIROR'S FILE
Author:Buol, John M.
Publication:American Gunsmith
Geographic Code:6BURK
Date:Jan 1, 2019
Words:478
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