The Single Biggest Issue with the M4A1: The Magazine

For Force Mod Friday, we are going to be discussing the primary point of failure in the M4A1: The Magazine.

The primary cause of double feeds is a magazine that is not within specifications. When the feed lips are too wide, it can cause potential double feeds and induce malfunctions. ‘That’s great.’ You say, ‘but how do I check to make sure the magazines are within spec?’ enter the feed lip wear tool.

The feed lip wear tool (NSN 5120-01-574-0036) is designed to check the width of the feed lips, ensuring they are at the optimum location for feeding the rounds. To use it, you place it on the back of the magazine and press down on the follower. If it stops at the ‘go’ side, the magazine is good. If the tool goes all the way down to the ‘no go’ side, the magazine is defective and needs to be turned in. Pictures two, three, and four illustrate this for us.


When the magazine is turned in, it needs to be identified in such a way as to make it undeniable that the magazine is defective and will no longer be able to be used as a magazine for a weapon. If not, the supply sergeant will see a ‘good magazine’ and issue it back out to another Paratrooper.

Along with checking the feed lip width, you have to check and make sure that you are using the appropriate magazines. Picture five illustrates which magazines currently are in the arms rooms across the Army. The rightmost magazine is no longer authorized for use. The middle two are allowed to be used until attritted. That means that once they are no longer functioning, they need to be turned in.  The magazine on the left is the current enhanced performance magazine, which is the authorized magazine for the M4A1.

In addition to the EPM units are now authorized to requisition polymer magazines with the NSN 1005-01-615-5169 (BLACK) and NSN 1005-01-659-7086 (COYOTE TAN) as Additional Authorization List (AAL) items for the M4A1. The Magpul Gen 3 magazine does not replace the EPM magazines, merely augment them.

Magazines need to be checked while loaded and unloaded. Ideally, a paint marker should be taken to them, and they should be numbered. This makes it easier for the Paratrooper to identify which magazine is defective, and when it is, pull it from rotation. Maintenance needs to be conducted on them by pulling the base plate and follower to clean them. This also helps to prevent misfeeds and jams.

Long story short, know what you are feeding your weapon. It can mean the difference between a weapon that functions perfectly, and a weapon that jams non-stop.

#weaponsmastery #magazines #checkyourstuff

Special Thanks to @SoldierSystemsDaily for the pictures of the Magazines.


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