Magpul has just filed a patent application (#20100126053) for a quad stack AR-15 compatible magazine.

The design is quite straight forward. A central partition separates two dual staggered round stacks. Two springs are used, a lower stronger spring and a weaker top spring, which are joined by spring slicer.

The magazine has a constant curve geometry. Interestingly, the transition area (16) is asymmetric in order to stagger rounds correctly.

The follower

The follower is very interesting. Two bails (58a and 58b) are spring loaded. When the follower is pushed against the central partition they part and reveal a hole which allows the follower to descend below the partition.

The patent does not reveal what the capacity of the magazine would be. I would expect it would be around 50 rounds.

The patent application comes on the heel of the announcement from Izmash that one of the major features of the AK-200 will be a 60 round quad stack magazine. It seems 2010 or 2011 may be the Year of the Quad Stack Mag!

A quad stack magazine would be ideal for the M27 IAR. I have no doubt that Magpul will eyeing a lucrative contract with the USMC.

You can read the full patent after the jump.

UPDATE: Drake at Magpul said to me “Unfortunately I am unable to disclose any other info at this time on the product in question.” (more…)