Re: steel base and aluminum rings issues?
The key thing to remember is what is going on at the hottest interface. On a bolt action rifle with a steel receiver, a one piece rail is pretty straight and stiff in the axial direction. So if you use an aluminum rail on a steel receiver and fit it at 75F and then go hunting at 10F the rail would have shrunk a lot more than the receiver ans this can set up stresses to the point where the rail could be deflected, even if this is elastic. This would shift the point of impact.
Take the same rifle shooting prairie dogs and the barrel could get pretty hot, now the rail would expand more than the barrel and deflect the opposite way.
Where the rings attach to the scope base, they are much closer together than the rail overall length, so the total dimensional change is less. Consequently, even though the scope tube is aluminum, with the rings being close together less deflection will be taking place and at some point a change in impact would not be measurable.
I just make sure to match the scope base material to the receiver and loctite it in place. I would agree to be careful to use steel rings on aluminum, the steel will win every time. I don't see any reason to use rings strong enough to lift an SUV on a battle rifle. There has to be a weaker component in the scope or the scope tube will simply crush before the rings let go, so what is the point ?