I have a Vortex 4.5 by 27 scope, I'm wanting to add more moa into the system on top of my 20 MOA rail. Can I add 25 more MOA to the system and still be able to zero at 100 yards?
It all depends on how much elevation adjustment your scope actually has. If you have more than 45 moa than you should have no issues with a 45 moa mount. If you're right there than it will be questionable.
If that's the case even if the tube is clocked perfect 35 is going to be about max, depending a few things. If he's going to use the very top part of a good ret he can add more, an still get a 100 zero.