Корпус окончательно утвердил запрет на использование коммерческих пластиковых магазинов. Основная причина, конфликты в подаче у M27 IAR.  IAR предназначен для замены M249 и сейчас активно закупается. Хотя ходят упорные слухи, что настоящая цель - замена M4.

Polymer rifle magazines, preferred by many combat troops for their durability, have been banned by the Marine Corps, according to a new administrative message published Monday.

Effective immediately, only standard-issue 5.56mm metal magazines are approved, according to the message, signed by Lt. Gen. Richard Mills, the Marine Corps’ deputy commandant for combat development and integration. They have a 30-round capacity with either tan, green or black followers, the internal plate that pushes rounds into a rifle’s chamber.

The message announces a handful of updates stemming from the Corps’ most recent marksmanship symposium, held in October. Marine officials reviewed everything from approved combat equipment to marksmanship training and education.

The polymer magazine ban is likely to upset Marines who tout their superior durability. Traditional metal magazines do not spring back once they are bent, meaning they may not feed rounds properly to the weapon — a grave concern in the heat of a firefight.

Some manufacturers of polymer magazines claim their products still function properly after routine bumps and drops, being rolled over by heavy tactical vehicles and, in some cases, after being penetrated by a bullet.

Marine officials began ad hoc bans on polymer magazines last year, citing concerns over their lack of compatibility with select weapons. The new message from Mills, who doubles as the commanding general of Marine Corps Combat Development Command, makes the ban official across the force.

While they work well in standard M16 and M4 rifles, polymer magazines present potential problems when used with the Corps’ new M27 Infantry Automatic Rifle, which is being fielded throughout the force as a substitute for the M249 Squad Automatic Weapon in some formations. More than 5,000 M27s have been delivered to the Corps, with many in the hands of deploying Marines. An additional 1,400 are slated for delivery in the months to come.

The M27 has unique tolerances in its magazine well that can prevent polymer magazines from seating correctly, resulting in failures. That poses the risk for malfunction should an automatic rifleman share magazines with his squad members during a firefight. Metal magazines are standardized across the Corps’ 5.56mm rifles.

Companies that produce polymer magazines are releasing new products they say are designed fix compatibility issues. This summer, for instance, Magpul released its third-generation polymer magazine, which it bills as compatible with the M27. It remains to be seen whether this may sway the Corps to reverse its ban.