LHSmith said:
#2/ The Parallax adjustment is best done by dialing all the way below 100 yd mark ...and then slowly bringing it up (towards "100" mark) until all parallax is out.....IF you go past the ideal adjustment, it is best to go back down below "100" mark and start again.
Actually, it is just the opposite. To remove parallax (with a side adjustment scope), you need to start from the infinity end, and slowly come back to the range of the target.
There is slop in the mechanism of the adjustment, and you must make sure that the slop is such that when the rifle recoils, the erector cell does not shift into the slop, but is held in place because the slop is on the other side of the recoil direction.
With an adjustable Objective scope that does not have a locking ring, there is no need to worry, because the objective is spring loaded and there is no slop. If the AO scope has a locking ring, use it!
http://www.snipercountry.com/Articles/Parallax.asp