Hello Kansas,
I will be Travelling thru your great state(I was born here), and staying in Marysville next week for the 2018 Boss nationals.  My question is can I legally open carry an AR in a roof mounted rack in my truck?  Can I have a loaded mag inserted?  Would it be better to put under the rear seat?

Thanks

I don't honestly dont know about the roof mounted rack if it is visible.  You can certainly carry it around loaded in your truck without issue.  No restrictions in that regard unless you arent allowed to own it.  If it were me, the gun would be hidden.  I personally just don't like any more attention than necessary and an AR brings plenty of attention if someone notices it.  Perhaps even sticky fingers.