The POF-USA P-308 is a interesting rifle. It is a gas piston operated rifle, based on the AR-10/AR-15 design and requires no lubrication.
They achieve this by plating the upper receiver with silicon nickel and chroming and heat treating the bolt and carrier.
Here is a video of it in action
In spite of its name, it is chambered in 7.62X51mm, not .308 (yes, there is a difference).