This rifle is supposed to be a modular rifle that will be available in 5.56, 7.62(AK), and .300 BLK, and can accept AK and AR magazines.
http://www.thefirearmblog.com/blog/2014/01/07/sig-556xi-rifle-7-62x39mm-5-56mm-300-blk/
From: The Firearm Blog
