Explain short range impact of parallax...

[Bigeclipse]

All,
I believe I understand parallax but i am simply looking for what the consequences of using a scope which has parallax set at 100yards on a squirrel hunting rifle shooting at 20-75 yards? Everywhere I read people say you want a scope with parallax set at like 50 yards in that case but they don't say what the consequences are if you use a standard scope. The reason I ask is right now my cz455 where's a Burris 22mag scope which is ok at best. I have a bushnell elite 4200 2.5-10x40 laying around and was thinking of throwing that on since the glass is so much better but if it will really hurt my groups at shorter ranges for squirrel hunting then I won't do it. For example if my groups at 50 yards will open up by 1/4 inch then I don't care but if suddenly my bullets could be off by a half inch or more then I might care because the kill zone on a squirrel is rather small. Thoughts? Thanks.

 

[Bigeclipse]

Maybe this is a dumb question. Is there no one that can comment

 

[el matador]

Its hard to say exactly since every scope is different. But in general your parallax error will increase with magnification, and it will be an angular error (such as MOA). At close range and using low power there probably won't be much error.

The bigger concern for shooting at close range is the focus. Parallax happens when the reticle and the target are not focusing on the same plane, so one image or the other is going to appear blurry. If your scope is set to have both images in focus at 100 yards it might not be in very good focus at 20 yards.

The best way to find out if your scope will work is to try it out. Point it at an object 20 yards away on low power. Are the reticle and image both in good enough focus? When moving your eye side to side does the reticle appear to move excessively with respect to the target? These tests will let you know exactly how your scope will perform at close range. Good luck, and nice choice on the CZ.

 

[MudRunner2005]

My whole life I have always used a regular centerfire rifle scope on my rimfire rifles, never knowing that standard centerfire scopes have a set parallax at 150 yards, and I never had a problem. Recently upgraded my scope on my 10/22 with a new Nikon Rimfire II 4-12x40 BDC 150 designed for the .22LR. After purchase I found out the internal (non-adjustable) parallax was set for 75 yards, which sucks, but that's such a short distance between set and zero, that I should have no issue, and I'll just sight it in at 100 and be done with it, like I always have.

Here's a good explanation of parallax...

[ame]http://www.youtube.com/watch?v=1VPGcq9IVxc[/ame]
[ame]http://www.youtube.com/watch?v=6ziKTDIMCig[/ame]

 

[Bravo 4]

I'm with el matador on this one, you can check to see movement of reticle at different ranges. It says that in the first video (didn't bother watching the second) as well I believe. I do not agree with a couple things in that video, as I believe some of the info expressed isn't entirely correct. All red dot scopes are not parallax free and using vignetting (black circle around reticle when backing your head away from optimal eye relief) doesn't always work either. It is a decent technique for when your reticle is near center of the tube, but crank the turrets for a LR/ERL shot or have a good cant built in and the reticle is well off center for a close shot and you will find it difficult to get an "even" black ring around reticle. Or try it with a scope that has a tricky eye box. I would say your best bet is to set the rifle up so you naturally are centered behind the scope, then you won't have to worry about parallax.
But in all honesty brother I think you are overthinking it.

 

[Canadian Bushman]

I can tell you this. Parralax and focus are not the same thing. You cant judge a riflescopes parralax by the clarity of the image or the reticle.
Ive had scopes thats focused beautifully but still had parralax, and needed to move back out of focus to get rid of the parralax. Not real common in high end scopes but it does happen.

Now to directly answer you question. Typically what is meant by the yardage where a scopes parallax is "set" is the minimum range in which the parralax can be removed. A number i feel a lot of mfg's lie about.

On centerfire rifle scopes this range is usually about 75-120 yds.
On a rimfire scope it is usually 20-50 yds.

If you havent noticed by now parralax is much harder to get rid of at close range. The movements required on the knob are very small. Where as at long range you can just about use the same setting for 1700yds as you did for 800 yds. This is how the trend of having a four inch parallax knob with 5yd increments on a rimfire scope came about.

If you really wanna dig into it. Google "depth of field" and read around about camera lenses and focal planes. A conversation with a photographer really opened my eyes about rifle scopes.

Easy way to solve it and save some money, use a fixed power scope.

 

[ShtrRdy]

I think the best way to get an answer is set up a target at 50 yds and set up your rifle in sandbags or something else to hold it steady, then pick a point on the target and move your head slightly up/down and left/right to see how much the crosshair moves over the target. That will be your possible aiming error.

 

[HARPERC]

......I would say your best bet is to set the rifle up so you naturally are centered behind the scope, then you won't have to worry about parallax.
But in all honesty brother I think you are overthinking ........

This would be my understanding as well.

 

[Bigeclipse]

Thanks everyone for the comments. I decided to say "screw" it and took thither scope off and slapped on the better scope. All I can say is what a difference. Clearer sight picture at both short and long ranges. I can easily hit 2inch targets at 25, 50,and 100 yards so I am simply going to call it good for small game hunting rifle. Thanks!

P.S. I cannot state how pleased I am with the CZ455. The trigger breaks nice and crisp at 3lbs. I did buy a spring kit to make it lighter but so far is not needed as it is so crisp and nice I don't want to mess with it. I have tried numerous kinds of ammo both bulk and higher grade stuff and the worst 5 shot groups were about 1MOA which for a non-custom 22lr is great out of the box. The bulk CCI standard velocities are giving me very consistent .5-.75inch groups at 100 yards (assuming little to no winds).

 

[redbullitt]

Glad to hear it! The parallax issue can really come into play for air rifles... They are shot at much closer distances and many scopes simply cannot focus or work well so close.

You can generally see the parallax error by keeping the rifle stationary but varying your head position. Some optics are worse than others, and higher power adjustable ones seem to be even more noticeable,

They say you should never skimp on the scope... your rifle is only as good as your optics. I would rather have a 2 moa rifle with top notch optics than a .2 moa rifle with an inconsistent scope ( provided I could not take the good rifle and swap on a good scope lol).