Found this in The Firearm Blog today:
http://www.thefirearmblog.com/blog/2018/03/25/spike-416-spike-a-308-version-of-300blk/
So I looked around a little:
Thanks to Shawn and Brian of 2AGuysandGear. I almost missed this at Big 3 East but Shawn mentioned it and showed me a photo. So on the last day I caught up with Spike’s Tactical. They brought out a new caliber to show us. It is called the .416 Spike. It is basically a .308 version of .300 blk. I had actually pondered this a while back and at the time there wasn’t a larger version of a .300blk. Well now there is.
http://www.thefirearmblog.com/blog/2018/03/25/spike-416-spike-a-308-version-of-300blk/
So I looked around a little: