Only if you want to change it to a different MOA....
I don't see why you'd want anything other than steel. Al and Ti are lighter, but softer, and it doesn't sound like you're looking for a lightweight rig.
Some people bed their rails to their actions....just FYI. Commence innuendo, now.
So. . As hard as steel and bedded to the action. That about right?
Methinks you've been sensitized to the double-entendre sufficiently already,
All joking aside (for a moment, only), I've had fasteners loosen due to loss of pre-stress with a loss of torque. With base materials unable to withstand compressive forces from the fasteners, they yield, deform and the connection is compromised. Steel is much harder to deform than non-ferrous materials and in particular changes size much less with temp extremes than Al, as an example. This part I have somewhat of a handle on, so I don't disagree that steel seems ideal for a rail material. Aluminum can also "creep" over time and continue to move even if the forces aren't increasing.
Where I'm shaky is to why differing MOA (Minute Of Angles) are required on the rail. All I can think is that not all scope tubes are mounted parallel to the receiver surfaces. Perhaps to set them to the bore line instead?
My knowledge is weak here and I won't expect you to become responsible for my edification. Google is my friend.
Always a "pleasure" discussing things with you.
Inoxy
PS: Thanks for the PM heads up.