RE: 300 yard Sight In for a 300 Win Mag
Fred, go into google and search for point blank range. This will give you an approximate sight in for a given target size with a cartridge of your selection.
Example: a 10" target using a 300 WM, sight in at X" at 100 yds. Point blank range will be XXX yds. Which means you can hold in the center of the target and the bullet path will not go above or below the target at any range from 0 yds to the PBR given.