Have you shot it at 100 yds, or maybe even 50 yds, Just to see where your at? One of the things that need's to be understood, if you can't shoot a decent group at 50 yds, then you can't at a hundred. And if you can't shoot a decent group at 100 yds, you can't at 200 yds.
If you took a brand new rifle out to sight in and immediately went to 300 yds because that's it's point blank range for the load your using, you'll become very frustrated just trying to hit the target.
It really does sound like you need to back up to 100 yds and then do some load development. I just checked the Nosler manual and the top load listed is just UNDER 3000 fps. Your just over, where did you start load development?