adjusting parallax without AO?

[Axis II]

I have a bushnell 3-9-40 with illuminated reticle I was told I can adjust the parallax by taking the front ring off and adjusting it.

is this possible?

I was thinking put it for 50yards as this will be used on a 22lr for squirrel and coon hunting.

any info is appreciated.

 

[ironworkerwill]

I think I'm dense, what front ring? The one that holds the objective lens?

 

[jmr40]

Don't worry about parallax. As long as your eye is directly behind the scope it is not an issue at all. At worst you're talking about a tiny fraction of an inch at 50 yards. Probably less than the diameter of a 22 caliber bullet. Most guns, rifles, and shooters aren't good enough to notice.

 

[Axis II]

Don't worry about parallax. As long as your eye is directly behind the scope it is not an issue at all. At worst you're talking about a tiny fraction of an inch at 50 yards. Probably less than the diameter of a 22 caliber bullet. Most guns, rifles, and shooters aren't good enough to notice.

I'm not sure but I was told if I have it cranked to 9 x trying to find a shoot a small target it won't be clear cause parallax is set for 100 yards. I guess I'm trying to keep it clearer for a closer target.

 

[Axis II]

I think I'm dense, what front ring? The one that holds the objective lens?

Yep some it's just a lock ring some it's got the lense in it

 

[ironworkerwill]

That would definitely be out of my comfort zone. I'd be afraid of letting the gas out.

 

[Walkalong]

I was told if I have it cranked to 9 x trying to find a shoot a small target it won't be clear cause parallax is set for 100 yards

It will be clear as far as your eyes can see. As posted, if your eye is directly in line with the scope, there is no parallax, and even when it is a bit off the difference is tiny. Don't worry about it. There is absolutely no need for a parallax adjustment on a 3X9 scope.

Some will disagree, but IMHO there is no need for it on a hunting scope at all. Now maybe if you are making long distance shots where you have plenty of time........

 

[I6turbo]

I recommend you give it a try. I adjusted my Sightron SII 3-9x42 from the factory 100 yards (that's the factory spec - I didn't test it to see what it was actually set for) down to about 50 yards. It made enough difference in focus and image clarity at shorter distances that it was easily noticeable and I would definitely do it again. Making the adjustment improved the focus and made the image sharper, which I wasn't expecting.

 

[Bart B.]

Do your own short range tests. As Walkalong states, the error is small.

To keep scope internal stuff intact, have an optical shop make a .03 diopter lens to fit the objective lens bell with a Butler Creek lens cover keeping it in place. It'll focus the scope at about 36 yards giving minimal parallax error from 20 to 60 yards.

A diopter is an old metric system unit for lens magnification and focal lengths. One diopter lenses have a focal length of one meter; about 40 inches. Dividing 1 meter by a lens' diopter value equals it's focal length. 1/.03 = 33.3 meters, about 36 yards.

I used one on an old Weaver J4 scope atop a Rem 521T rimfire 22 in the early '50's.

 

[wally]

With some inexpensive scopes, adjusting the rear diopter to bring the target in clearest focus can help.

By the "book" the rear diopter is supposed to be adjusted for the clearest reticle when looking at a featureless background (white wall or clear sky) when your eye is relaxed (focused at infinity) so your vision doesn't adjust (accommodate) when going from the distant target to the scope. Since the reticle is unlikely to be focused at inifinity (although some Russian 4X PSOP type scopes appear to be) scopes usually need the diopter correction for your near vision.

If you've not done this for your scope, I'd try it first and only if it doesn't help try the "focus the eye piece on the target" trick.

Taking off the front or rear ring is a good way to ruin a scope, but feel free to play with any adjustments to see what works best for your situation. Most people just want a nice "compromise" setup so they can see a target and shoot without futzing with scope settings -- bench-rest and match shooters excepted, although they pretty much universally use adjustable objective scopes.

 

[Bart B.]

How does the scope's eye piece (rear diopter?)have a reticle focused at infinity when they're about a 20 diopter lens with a 2 inch focal length for reticules in the second focal plane at the reticle is about 2 inches in front of the lens optical center?

 

[wally]

The reticle is not "focused at infinity" (in terms of vision "inifinity" is about 6m or 20' distant) the adjustment is to have your eye be relaxed which would be focused at infinity for "normal" vision, then the diopter is adjusted so the reticle at its apparent viewing distance is in sharp focus with your eye relaxed so it doesn't need to accommodate.

My wording about some of the Russian PSOP type scopes was sloppy, the apparent viewing distance of these reticles is much closer to optical infinity than most any other scope I've ever looked at. I really noticed it when my Presbyopia was getting really bad (before I had Lasik) and I was running out of adjustment on most scopes except the PSOP where the reticle was still nice and clear despite it not having any adjustments.

The apparent viewing distance of the image is often outside the instrument -- SLR cameras optical viewfinders for example

 

[Walkalong]

The scopes eyepiece is for focusing your eye on the reticle.

https://www.leupold.com/life/help-desk/how-can-i-focus-so-the-reticle-is-clear/

 

[Bart B.]

^
Yes. If you try to focus your aiming eye on the target adjusting the eyepiece, your eye will try to focus only the reticle. When the scope's objective lens focuses the target image on the reticle, there's no eye strain when the eye piece is focused on the reticle.

 

[imashooter]

50 yard zero w/ a 3-9 scope for squirrels and coons? You're kidding.

 

[Bart B.]

If he zeros high speed hollow points at 50 yards, impact above or below point of aim won't average more than 3/10ths inch at ranges from 17 to 55 yards. I think he knows exactly what he wants to do if that's the range band he'll shoot in; therefore, he's being quite honest and logical.

 

[Axis II]

50 yard zero w/ a 3-9 scope for squirrels and coons? You're kidding.

not trying to pick a fight but what's wrong with that?

some of our oaks get pretty big and sometimes I sit against a tree and pick them off while on the ground or other trees. coon its normally all tree shots so 25yards would work.

 

[Axis II]

If he zeros high speed hollow points at 50 yards, impact above or below point of aim won't average more than 3/10ths inch at ranges from 17 to 55 yards. I think he knows exactly what he wants to do if that's the range band he'll shoot in; therefore, he's being quite honest and logical.

you lost me bart.

 

[Bart B.]

Sorry 'bout that.

Here's a trajectory chart for a Remington 36 gr. HP Golden bullet leaving 1280 fps. With the scope 1.5 inches above the line of sight and zeroed for 50 yards, I see the bullet crosses a point about 3/10ths inch below the line of sight at about 15 yards, is above the line of sight about 2/10ths inch at 37 yards then below the aim point about 3/10ths inch at 59 yards. That gives a "point blank range" band 6/10ths inch wide vertically from 15 to 59 yards.



Does this help?

 

[Axis II]

Sorry 'bout that.

Here's a trajectory chart for a Remington 36 gr. HP Golden bullet leaving 1280 fps. With the scope 1.5 inches above the line of sight and zeroed for 50 yards, I see the bullet crosses a point about 3/10ths inch below the line of sight at about 15 yards, is above the line of sight about 2/10ths inch at 37 yards then below the aim point about 3/10ths inch at 59 yards. That gives a "point blank range" band 6/10ths inch wide vertically from 15 to 59 yards.

View attachment 225429

Does this help?

honestly not a bit. I will have to do some research on line of sight and such. my theory on your post is anything 15-59 yards I should still be able to hit it?

im somewhat new to the rifle, scope thing.

 

[Bart B.]

Yes, you'll be right on the money or on the medal platform. If your rifle and that hunting ammo shoots inside 3/4 inch in that 15 to 59 yard range band, farmers may pay you money to eradicate pesky animals like they did for me back in the early 1950's. I got 25 cents a head for squirrels in northwest Oregon nut orchards. Spent it all foolishly.

If you zero at 60 yards and accept a 1/2 inch above/below point of aim, you'll have a point blank range band from 11 to 68 yards

 

[Axis II]

I'm putting the 3-9 on the 22 tonight and we shall see what it does in the morning. I shoot cci standards and federal auto match and sometimes thunderbolts.

I like the 9x because sometimes the squirrel will lay on a limb and I like headshots for the meat and its hard to see just that half dollar size target. should I sight in at 25 and shoot at 50 and 25 to see if POI changes?

 

[Bart B.]

You betcha, Red Rider.

Actual shooting is best because it's got more variables to change bullet paths than even the best math based calculations.

 

[imashooter]

not trying to pick a fight but what's wrong with that?

some of our oaks get pretty big and sometimes I sit against a tree and pick them off while on the ground or other trees. coon its normally all tree shots so 25yards would work.

Sorry for the delay. Nothing's wrong. Just can't imagine having that type of shot at squirrels / coons. Bet it's fun. Don't know if I've ever gone past 10 yards.