Parallax vs Focus

[wapiti13]

Confusion of parallax vs focus isn't being helped by the scope companies. Leupold, Sightron, etc. have put the parallax adjustment on the left side of the turret and call it "side focus" in their advertising and descriptions of the new scopes. [img]/ubbthreads/images/graemlins/shocked.gif[/img]

[hareng]

Two years old but a good thread.

"If the reticle seems to move, there is parallax". So by turning the side wheel on a long depth of field scope it would become parallax free at whatever you are looking at.
Now on shallow depth of field scopes, either side of the parallax setting will be a blur. For instance at 50 yards it will be a blur when looking at something at 53 yards, or 300 and 325 yards! Now setting the pa for infinity whilst looking at close stuff, the ret dont appear to move infering that it focuses on the target as it is already parallax free. Checked clamped in a miller at varying ranges.
I have used an M1 Mark 4 for 5 years, and just about every scope out there and work from low to high as do 100's of people i know and have seen- get the range 2% out and its a miss. Always work from one direction, back it off a bit and try again until satisfied even if its got severe backlash.

I on the other hand have seen and had the misfortune to own/use parallax uncorrectable scopes even though the pa wheel is in focus on the target within a yard- Even at at 50 yards there was 3/4"+ off centre ret movement in all directions dependant where head was, yet alone at a 1000 yards. Had 5 replacement scopes and two repairs nine years ago, all the same. Just intrigued was it incorrectly adjusted/set internally?

[LandToSea]

Hey guys! I read your string of posts and found them quite informative as I am currently setting up my new Leo Vari-XIII 3.5-10x40 LR M3. I used Catshooters instructions for setting up the scope and ran into an issue when trying to zero the AO side knob. I focused in on an object at aprox 400M (the farthest I could conveniently find without obstruction) and played with the AO knob as Catshooter instructed. I started at infinity and worked my way back until I was parallax free. I was concerned that this point was at the middle dot on the adjustment knob so I went thru the process again starting back at infinity. The result was the same so I loosened the screws and reset the knob so infinity lined up with the hash mark. Now the knob bottoms out at the low magnification end around the second dot and consequently turns way past the infinity mark on the top end. I called Leupold to ask their feedback and the WOMAN who answered the tech line basically said that the knob is set at the factory and not meant to be adjusted. I obviously mentioned that there is adjustment screws on the knob which usually means they are there to enable adjustment but she stuck to her limited insight. I knew I was not getting anywhere so I came back here to ask the gurus for their guidance. [img]/ubbthreads/images/graemlins/confused.gif[/img] Please advise. Thanks!

Good information. One thing to note is that not all a/os have lock rings! Leupold learned the importance of the lock ring on their later BR-D model and added a second spring to try to keep the BR shooters happy. Didn't work - keeping them happy that is....

So we can safely say parallax exists in all scopes when viewing at distances outside of the parallax free zone - usually 100yds on North American hunting scopes.

If your shooting at 300 yards plus and are doing it for score on targets you want to eliminate parallax unless you like giving your competitors who have A/Os or Side focuses the advantage [img]/ubbthreads/images/graemlins/grin.gif[/img]

Next time your at the range bag your gun and check out the effects of parallax at the different yardages! You'll be surprised, but look to 300 + yards to see the real impacts. You can see them with your 6-20x set at any power in its range. If you like you can even compare or measure the degree of movement at the different powers not only at the max power....

If you can fix your eye to be at the same location each time you pull the trigger, parallax is not an issue. Unfortunately, this is impossible!! [img]/ubbthreads/images/graemlins/grin.gif[/img]

[700]

Guys & Girls

I have a spread sheet done in Excel which may help people understand the relationship between magnification, objective diameter and parallax.

If anybody wants a copy just email me at brXXXian_sinXXXnott@hotXXXmail.com.

Remove the Xs from the email address.

Kindest regards

700

[LandToSea]

Regarding my previous post I was hoping for some response from Dave and Catshooter
Hey guys! I read your string of posts and found them quite informative as I am currently setting up my new Leo Vari-XIII 3.5-10x40 LR M3. I used Catshooters instructions for setting up the scope and ran into an issue when trying to zero the AO side knob. I focused in on an object at aprox 400M (the farthest I could conveniently find without obstruction) and played with the AO knob as Catshooter instructed. I started at infinity and worked my way back until I was parallax free. I was concerned that this point was at the middle dot on the adjustment knob so I went thru the process again starting back at infinity. The result was the same so I loosened the screws and reset the knob so infinity lined up with the hash mark. Now the knob bottoms out at the low magnification end around the second dot and consequently turns way past the infinity mark on the top end. I called Leupold to ask their feedback and the WOMAN who answered the tech line basically said that the knob is set at the factory and not meant to be adjusted. I obviously mentioned that there is adjustment screws on the knob which usually means they are there to enable adjustment but she stuck to her limited insight. I knew I was not getting anywhere so I came back here to ask the gurus for their guidance. Please advise. Thanks!

[270WSM]

To me, it sounds like you just set your knob so that your infinity setting is at 400 yards. I know my Nikon tactical at the lowest setting is parallax free at 50 yards (advertised and tested by me). I setup the rest by finding objects at 100, 200, 300, 400, etc.... and figuring where my paralax setting for each was and made a scratch in the side parallax wheel. Make scratches where you see fit (the further the distance, the closer the scratch marks will be so you have to decide what yardages to scratch in). I don't see why you need to loosen the set screw and do all that?????? Good luck with which ever way you go.