When I set as closely as possible the parallax setting on my scopes for 300 yds., I'll get groups from .87-1.5 inches with my rifles. But at the same parallax settings, I no longer get any groups much under .6-.7 @ 100 yds. But if I set the scope to be as parallax free as possible for 100 yds., I do get groups down into the .3-.5 inch areas.
It's all well and good to talk about placing your head directly behind the scope to eliminate parallax. I, for one, have never been able to achieve that. E
