Parallax adjustment or no parallax adjustment

Please help me out here long-rangers; in your experience do you need a focus adjustment on your scope to knock out parallax for longrange or not ?

To narrow things down a bit; shooting out to 600 metres only (probably close enough to virtual infinity), focus adjustment either on the side or via a threaded objective, either way getting the image and reticle into the same plane for zero parallax. Assumes hunting situations rather than bench where always getting a perfectly consistent cheek weld / eye position is not possible. Maybe include the magnification, or perhaps just the scope type, for example is the S&B 3-12x50 PM II useable or does it need to be a 3-12x50 PM II/P ? Leica in changing from ER to ERi have moved from a side focus on the ER 3.5-14x42 to not having an adjustment on the replacement ERi 3-12x50. Do these two examples indicate 12x as the accepted cut-off point perhaps ?

For the above mentioned S&B the calculated maximum parallax error with the shooters eye offset to the edge of the exit pupil for a 600m target is 25mm, and 125mm ( 0.7moa ! ) for the Leica. The difference is because the S&B is focused for 300m, the Leica at 100m. For a 1mm offset in the eye position off the optical axis at max power (12x) the reticle moves 12mm and 60mm against the target respectively. In my opinion Leica really should reset the focus from 100m to 300m for the 3-12x50 variant with target turrets (or better still retain the focus adjustment).

60mm is getting up towards 0.5moa error at 600m. That is for the eye just 1mm off axis. Does this mean the search for accuracy in the load and rifle is questionable with a scope like this ? These figures still don't give an indication as to how parallax is experienced at a practical level. Maybe getting the eye exactly in line consistently is easy ? I've never really given it much thought having had focus adjustments, but I'm now looking at scopes without.

Bump. Still asking.... any views on when a scope needs a parallax / focus adjustment, and when it doesn't ?

I have one with parralax adj and one without.
I don't/can't tell the difference in accuracy.
Decent cheek weld your eye should be in the same spot, pull back to the end of the eye relief (where you should be away unless you like scope eye) and its plainly obvious if your eye is not centered.

Its normally 10x and above that most would say needs a adjustable parallex , as to the the PMII with out the side focus para knob, I would not worry too much about not having it .
You should not disguard a 3-12x50 PMII , just because it dosnt have a side focus , BUT it should be cheaper than one that has the side focus , and you probalily know that already .
If you can geta good deal on it with out para , get it , and move on .

Later Chris

Thanks VC and Chris for the replies. Looking at Leica options where currently only the 2.4-16x56 Magnus has retained a focus adjustment. The rest have fixed focus, and unfortunately all of these are set for 100 metres rather than 300 metres ( S&B ), target market must be hunting rather than longrange/tactical.

Consider whether you will be able to focus clearly on the target. Parallax adj allows you to focus the target clearly at all ranges. People over 40 find it progressively harder to focus up close. The lens in their eye goes hard and they stay focused close to infinity ( or whatever depending If they are short or longsighted). If you have had a cataract fixed or are over 60 you will find it very noticeable at short range ( <100m). Using a SB 10x40 it was a nice scope but blurred up close. You might also find the image unfocused at infinity perhaps you're not actually shooting that far but annoying. My vx1 2-7x32 has fixed parallax at about 80m and is always blurred a little at the horizon. I went for parallax on my 3-12 PM II and when set at min of 50m it is quite use able down to 20 but blurry at 15m on 12x. Vrry much nicer to use for me. If you are 20 yr old and not long sighted then without parallax will be OK.

Understood Bagheera and thanks for the reply, another good reason for having adjustable focus over fixed, and the decision has been made and I've opted for adjustable. Now I need to confirm that best focus does in fact correspond with no parallax at a given range - in theory of course it should.

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Originally Posted by Bagheera

Consider whether you will be able to focus clearly on the target. Parallax adj allows you to focus the target clearly at all ranges. People over 40 find it progressively harder to focus up close. The lens in their eye goes hard and they stay focused close to infinity ( or whatever depending If they are short or longsighted). If you have had a cataract fixed or are over 60 you will find it very noticeable at short range ( <100m). Using a SB 10x40 it was a nice scope but blurred up close. You might also find the image unfocused at infinity perhaps you're not actually shooting that far but annoying. My vx1 2-7x32 has fixed parallax at about 80m and is always blurred a little at the horizon. I went for parallax on my 3-12 PM II and when set at min of 50m it is quite use able down to 20 but blurry at 15m on 12x. Vrry much nicer to use for me. If you are 20 yr old and not long sighted then without parallax will be OK.

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I'm 64 and a good pair of glasses fixes all!:thumbsup:

Unless you dial away the parallax movement (when you deliberately wobble your head about to see if the cross-hair is moving vs the target) then I say pulling the trigger is a complete mistake. Any dope you write down is skewed with incorrect data. For example you might begin thinking the wind is off, spin drift not right etc etc. Your handheld device (pda, cell or kestrel) is now giving you faulty info. Why? Parallax not being dialed away when you zero'd, and also when you set up for your 800m shot.

IMO you chose well to get an adjustable scope on the side. The AO thing just isnt ergonomic at all - you end up breaking that "took me friggen ages to get it right" shooting position just to reach forward to mess with the front objective lens. Stuff that!