Magpul is coming out with 60 round drum.
The PMAG D-60. Sixty rounds. Reliable, durable, lightweight, shorter than a 30 rd mag, and full of features that make it extremely easy to use. MSRP $129.95. Please note that transparent back and cut-away versions were for testing purposes only, and the solid drum with round indicator window is the variant that will be offered for sale. Shipping Spring/Summer 2015.