What sight are you using?
The sight in the picture is a Trijicon Reflex. Right now, I have a Primary Arms M3 clone mounted.
I can't seem to decide which I like better, so they get swapped back and forth fairly often.
As for oiling the outside of the rifle... Parkerizing is a pretty durable finish, oiling is not really needed unless your in a salty environment.
The rifle pictured gets pretty rough treatment, and as you can see the finish still looks pretty good. Maybe once a year I hit it with Rusteprufe.