ARES Defense are selling a new 2012 version of the ARES Shrike 5.56. The Shrike 5.56 is an AR-15 compatible upper receiver that can be magazine or belt fed. I am not sure what the changes are from last years model.
The new 2012 Shrike 5.56 – Advanced Weapons System™ is a robust, ergonomic and lightweight upper receiver assembly that is designed to fit MIL-Spec quality AR-15, M16 and M4 type lower receiver assemblies. Once fitted to the host firearm’s lower receiver, the Shrike 5.56™ provides an individual operator with the firepower of a US M249 Squad Automatic Weapon (SAW) at one-half the weight of the current SAW.