Re: 20 MOA rail on 93R17
agree, it's flat enough that a decent modern optic on top would probably be good enough. i got a .22 mag that goes out to 275 before bottoming out on the optic, i imagine the .17 would probably be more like 350 to 375 before needing the help.
if you want, you could figure it out by running your data in a ballistic program, converting it to MOA you have to dial in, then figure out if you have that much adjustment left in your optic to compensate. at the yardage you run our of adjustment, that's when you'll need a base or MOA adding rings.