I would guess that your Sendero is like mine. My Sendero just does not like Hornady Bullets. I get 1/2 to 3/4-inch groups with Nosler Partitions & Nosler Accubonds. If you try the same load with Hornady bullets I get a pattern not a group.
I am lucky, I have an old Ruger M-77 300-win mag that just loves any bullet(except barnes-x) you feed it. I have been useing my Hornady's in it with good results.