The bullet drops about a foot at 200 yds, where retained energy has plummeted to about 600 ft/lbs. Read more
You might think about a .223 Rem. as Winchester loads a 64gn bullet and OSA loads a 63gn bullet.
I recommend sighting-in 3 inches high at 100 yds for a 250yd. zero and drop of 4 inches at 300.
Parallax can be detected by placing crosswires on the centre of a target at say100 yards, and while looking through the scope, moving your head from side to side.
I've also used the 130gn Speer spitzer in my 7mm-08 with excellent results at ranges from 50 to 250 metres.
It appears that the .270 WSM has about a 150 fps velocity advantage over the venerable .270 Winchester.
In 1986 Thompson/Center included it in their Contender line, both handgun and carbine.
For extended range conditions such as open country in the mountains or on the plains you should sight-in your rifle to zero at 200 metres or more.
Scope mounts pose no problem since the action is the Mark X Mauser.
It is a sloppy practice to fit Weaver rings in a 1913 rail because round recoil lugs aren't a snug fit in a square slot.