M13B = SIG-Sauer MCX VIRTUS (added with Season 1) Chimera = Honey Badger/SIG-Sauer MCX hybrid (added with Season 1 Reloaded)

The Chimera is a curious case in Call Of Duty: Modern Warfare 3, while it has the expected damage output of an assault rifle, its close-range optimisation is something more akin to an SMG. Whilst there are even more powerful options out there, the Chimera remains as one of the best assault rifles in Modern Warfare 3.