I would keep the barrel length the same and go with the YHM rail.
If you drop to the 6.5" barrel, you will see a performance loss on the 300. I seem to remember you stating that you like H110 in your loads. That extra 2 inches will be big in ensuring that most of the powder gets burned up instead of blasted into your can.
If you drop to the 6.5" barrel, you will see a performance loss on the 300. I seem to remember you stating that you like H110 in your loads. That extra 2 inches will be big in ensuring that most of the powder gets burned up instead of blasted into your can.