Nikon has a great scope for a .223 rifle, such as your AR-15. They call it the “M-223”. It’s slick and easy to use. It’s actually one of my favorite optics for any longer barreled AR build (Think Crusader Templar) or Varminter configuration.
What does Nikon have for AR-10/SR-25/Broadsword? Nothing so much… Right now for a Broadsword I’m thinking a PFI RR800.
What Nikon needs to do is a .308 specific scope, much like the M-223… but with an illuminated reticle.