Re: .300 WSM Browning X-Bolt
I have an X Bolt Composite Stalker in 300 WSM and love it!! As far as effective range goes the farthest I've shot it was 485 yards but at that distance it put 5 shots into just under 3 inches which is not bad at all for such a lightweight hunting rifle. I imagine she'll shoot well out to 700 yards which is the farthest I dare shoot with my current scope set up.
Your effective range can be increased using a higher BC bullet (assuming you can get them shoot well) like a 185 grain Berger, but if your rifle likes the bullets seated a little longer like mine does, than you'll need to use a Dremel or a file to open up the front of the magazine just a little to allow for reliable functioning so the bullet tips don't hang up in the clip. I've never shot long distance with the Hornady Interbond but I got great groups with both the 165 and 180 grainers at 100 yards and they fit into the magazine with room to spare, I imagine they'd be a good long range bullet for your setup.
I chose to put a Burris Black Diamond 4-16 with a Ballistic Mil Dot reticle on my X Bolt because I found one for $400 on the local classifieds and it allows for first round hits on big game out to about 700 yards. Again, the farthest I've used it was 485 yards on a target but the bullets hit right where they should have.
Previous advice that has been given is all good on your scope choice. I would personally take a long look at Vortex because I had a pair of their Kaibab binoculars and the customer service when i needed warranty work could not have been any better and the optics were superb. However, all my guns wear Burris scopes because I've found them for great deals and I love how much light they gather at the extreme limits of legal shooting hours.