....rings not withstanding,
......a 20 MOA rail is just that. The rear of the rail is a bit thicker than the front of the rail. I don't have the thousands specificarion close at hand but I believe a 20 MOA cant rail is around 0.017" thicker at the back than at the front, in other words tapered towards the front when sitting atop the receiver and 30 MOA is 0.027" or thereabouts.
EGW (Eveloution Gun Works) makes a variety of MOA cant rails for various rifles. I believe Midway sells their line.
EGW is an OEM supplier of parts to Savage. You'll find EGW rails and muzzle brakes
on Savage rifles in various calibers.
Not familiar with the Burris rings or the inserts. I use Warne maxima or Talley one piece.