Tomothy_Murphy,
No, I look through the scope at something 400 yards away, it's impossible to test for parallax at 400 yards by testing at 100.
Most big game scopes without parallax adjustment are set at the factory at 100-200 yards, but that will vary slightly when different people adjust the focus for themselves. Also, parallax isn't contant at any range, since it also varies slightly with atmospheric conditions. In effect, the air acts as another lens--the reason you might have to tweak the focus or parallax adjustment slightly on different days.
My favorite all-around scope for hunting out to 400 yards (or even farther) is the 6x36 Leupold, either the older M8 model or one of the new FX-2's. (In fact, I have them on most of my big game rifles in .25 to .30 caliber.) The 6x42's are also great scopes, and I have some, but the 6x36 only 10 ounces and is more than adequately bright, even the M8's. I realized that many years ago, when a new 6x36 proved much brighter than a Zeiss 6x32. (Theoretically this shouldn't have been true, because the Leupold was only single-coated, but another important factor in scope brightness is the reduction of reflection inside the scope, and Leupold is good at that.)
I've found it relatively easy to hold off for windage without hashmarks, using my knowledge of the subtension of the Duplex reticle.
