Scope question ........

[NUTT]

When you change your magnification from 3power to 9power on a scope does this move your impact point. My buddy shot at a buck on 9 power and missed him twice. He moved his scope to 3 power and later dropped a doe in her tracks. Someone told him he missed because he must have sighted his scope in on 3 power but shot at the buck on 9 power.

 

[HT2]

Nutt.....

I don't know about you point of impact......

But, you shouldn't shoot at such a high magnification........It makes that point of forgiveness even that much less.......

I would suggest that you shoot the same magnification while hunting as zeroing in your rifle.....

 

[edge]

reply

That could be a problem with lower priced scopes. Also, on cheap scopes, the windage and elavation knobs are less accurate and precise. This makes them harder to get sighted in. Not all will give problems, obviously, and I have even had this problem with a top of the line Swarovski. (Leupold is known for it's accurate adjustments. )

However, the guy probably just missed (or worse, didn't), the first time and connected the second time. Nobody wants to admit they missed!! But hey, it was an original excuse... . Just Kidding!!

er

 

[Buzz]

It can cause a change in POI but that change would be very small compared to the kill zone of a deer - especially at hunting ranges. I would guess you just missed.

 

[Predator56]

A quality variable scope shopuldnt shift enought to notice. Most are made to pretty tight tolerances. there is only one way to insure power change doesnt effect POI and this is more relavent in the tactical world not the deer hunters world... the answer is a reticle in the front plane which doesnt change with the power. that being said, 7x57 is probably right in saying that a rear focal plane reticle wouldnt change enough to miss a deer. I own scopes built both ways.

here is what i got off of usoptics.com:

"Why front or rear focal plane placement? Question: What are focal planes and what is the difference between putting the reticle in the front or rear focal plane? Answer: Only in a variable power scope is the reticle placement a major problem. In the rear focal plane, or behind the power changing lens system (erector tube), was the first solution that occurred to optical engineers, and most American scopes are still being built that way. Unfortunately, this apparently ideal solution has a very serious flaw.

Any tolerance change in the centration of the lens system and their spherical/longitudinal movement with the power change, will shift the point of impact. A variation of one thousandth of an inch will move the zero point approximately one inch at 100 yards. Since the mechanical parts that hold the power changing lens system slide inside each other, (some allowances are made for temperature changes, manufacturing tolerances and wear), there must be some movement made to accommodate this. Consequently this lateral and vertical movement will often shift zero by as much as several inches as power is changed.

A better solution is to place the reticle in the front focal plane, or ahead of the power changing lens system. The movement of the erector system will, optically, have no effect on the point of aim here. So why don’t all scope manufacturers build them this way? The downside of this method is that Americans typically do not like reticles that grow in size when the power is turned up. There is no actual growth in the reticle size. As the magnification increases, so does the reticle along with the objects in the field of view. A one inch dot reticle will still be one inch, at any power, be it low or high. It is only the appearance that is altered. If the power is turned from 2x to 4x, or doubled, the size of the objective image is doubled, and so is the reticle along with it."