The post below is from me a couple of years ago. I still stand by it with the caveat that parallax is a major error source when using high magnification at short ranges. Most applications using scopes for .22lr are going to be 100 yards and shorter. I cannot imagine using my .22 at 250 yards. For me it doesn't compute. If the 22 had a -250 behind it, that would make a world of difference.
Geetarman
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I am not sure I agree with your assessment of parallax and the effects of parallax on shot placement.
On scopes with non adjustable objective bells, parallax is generally set for 100 yards.
Parallax exists anytime the reticle and the target are not in the same focal plane and the apparent movement of the target and the reticle is significant at longer distances.
It is much more than just unscrewing the lens assy at the objective bell to "fix" parallax.
That feature is not built into lower quality scopes because it is expensive to do it.
The machining required to keep the objective bell internal thread axis parallel to the mechanical axis of the scope body is daunting. With out that, the shift of the reticle to a line of sight would give you a headache.
In any sort of optical tooling setup, proper establishment of a line of sight requires a set up at infinity as well as a close up target ( 2 feet or less ).
Without parallax correction, as soon as you buck the line of sight from infinity to the close target, you plunge and rotate the instrument and rebuck at infinity.
You will NEVER get a straight line of sight WITHOUT parallax correction.
If you have a parallax error of one arc second at 100 yards, you have an unknown of approximately 1 inch. That error gets proportionally larger as distance is increased if the end point cannot have that parallax error nulled.
On the other hand, a real error of 1 arc second at 500 yards is proportionally smaller as the range is decreased.
Parallax adjustments exist on high end scopes for a very good reason and that is not just so the manufacturers can charge more for them.
I did optical calibration for a major aerospace company for over 40 years and removing/reducing the effects of parallax is a major goal of successful calibration of alignment telecopes, jig transit squares and theodolites.
Geetarman