Parallax may be a problem...

[TM7]

Yet another parallax question...Well, I mounted an inexpensive 3-9 scope on my UV for initial testing. I'm new to scope shooting but will get use to it as my eyes aren't young. Anyway, I had good groups at 50 yds, but of course they opened up at 100yds. At 100 yds I noticed the crosshairs moved on the target; i.e. the crosshairs intersected different positions on the target depending on where my eye was in relation to the ocular of the scope without moving the rifle. Focus on the target wasn't bad. Is this an effect of wrong parallax adjustment for the yardage I was shooting or just an inherent scope sighting problem? Makes group shooting more difficult.....I do wear eyeglasses.


............................TM7

[Graybeard]

It could be as simple as you don't have the eye piece adjusted correctly. Or it could indeed be excessive parallax. You didn't mention scope brand so it's hard to know where the parallax is supposed to be set on it. On most intended for big game guns it is 150 or a tad more. Generally tho on a 3-9 it's fine and parallax doesn't become an issue. Over 9X it sure can.

First up do this. Loosen the locking ring on the eye piece. Glance at the cross hairs with gun held up against the blue sky or some other uniform surface a long way off. Don't stare into it or your eyes will adjust to the out of focus condition. If the cross hairs don't look sharp and clear and dark to you then adjust that eye piece a bit at a time until it does. Remember to just take a quick look each time so as not to let your eyes do the focusing. When you get this adjustment properly made try again. This adjustment is made incorrectly on the vast majority of scopes I see on other people's guns and when they correct it their shooting usually improves.

[gwhilikerz]

GB had some good advice . If you need a quick way to focus your scope take your gun to a room in your house that has a white wall. look thru the scope (look at the crosshairs). If they are not clear and sharp  adjust them until they are.  Don't be concerned about focusing on the wall. Just look at the crosshairs. When you have them focused sharp the job is done.

[quickdtoo]

Parallax explained by Leupold.

A Clear Understanding of Parallax
Often, people will pick up and use technical terms without really understanding their meaning. Take, for instance, the term parallax. How often have you heard people talk about parallax? Do you know what it means? Can you explain it to other shooters? If you can't, you're not alone. Many people are confused as to just what this term means. Quite simply, parallax is the situation that occurs when the reticle and the image are not in the same optical plane, causing the image to be unclear or to move in relation to the reticle. "Wait a minute, wait a minute," I can hear you say, "what's all this about optical planes?" Remember when you were a kid and you would burn a piece of paper (or a bug) with a magnifying glass by focusing the light of the sun on it? What you were doing was bringing the magnified image of the sun into the same optical plane as the piece of paper. Therefore, when you are bringing the image of the target into the same optical plane as the reticle, you are doing something similar; you are focusing the image of the target onto the reticle. Bringing the image into the plane of the reticle is important because if it is not in the same plane, the image will not be clear and reliable. Just as you had to move the magnifying glass back and forth to focus the image of the sun on the paper or it would be unclear of blurry and not burn the paper, so you have to move the lens of the scope back and forth to bring the image into the reticle plane or it will be unclear and not be useful. This is what we do in the Leupold factory when we set the parallax of the scope to a distance; we move the lens until an image that is a specific distance away, say 150 yards, focuses perfectly on the same plane as the reticle. You are doing the same thing when you adjust the adjustable objective or side focus dial of a scope with one of those features; moving the lens to focus the image on the same plane as the reticle. All of this is important because if the image and the reticle are not in the same plane, the image will be unclear and the reticle will appear to move in relation to the target. If either of these things happens, the result is obvious: you will not have a consistent point of impact. This becomes more important as the magnification of a scope increases - the greater magnification makes the focusing of the image more sensitive to changes in distance from the target. That is why lower magnification scopes are generally set at the factory for a specific distance and higher magnification scopes feature adjustable objectives or side focus dials. Knowing this and being able to explain it clearly will certainly inspire confidence in you on the part of other shooters. It will also help you in your own shooting activities, as you will better be able to understand how your own scope is performing.

[quickdtoo]

GB had some good advice . If you need a quick way to focus your scope take your gun to a room in your house that has a white wall. look thru the scope (look at the crosshairs). If they are not clear and sharp  adjust them until they are.  Don't be concerned about focusing on the wall. Just look at the crosshairs. When you have them focused sharp the job is done.

That's what GB explained, but you need to look away for a moment between adustments or your eyes will do the focusing and the adjustments you make won't work well. Unless the ocular lense is a fast focus type, it normally takes about ½ turn at a time of the ocular lense to adjust the reticle slowly into focus. A fast focus lense will only take fractions of an inch movement to do the same. The reticle should be instantly clear, dark and crisp when your eye enters the field of view of a properly focused ocular lense.

[quickdtoo]

Could very well be, but it could also be set wrong or damaged, too. Parallax is set at the factory and can be changed by the manufacturer and a couple scope specialty shops. Not practical for a simmons though, it would cost more than the scope is worth. I would suggest replacing it with a more reliable optic.