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Topic ClosedParallax-letting the genie out of the bottle again

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Direct Link To This Post Posted: January/07/2010 at 06:29
Time to make some pudding, Wouter!
"Peace is that brief glorious moment in history when everybody stands around reloading".
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Direct Link To This Post Posted: January/08/2010 at 05:08
Originally posted by 8shots 8shots wrote:

Nowhere in this thread did I talk about applying this information to any distance beyond 100m.

I'll give you that.  You hadn't yet, in this thread.
Originally posted by budperm budperm wrote:

He just likes to argue for the sake of argueing sometimes.

No I don't!!!!









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Direct Link To This Post Posted: January/08/2010 at 05:34
Originally posted by Jon A Jon A wrote:

[QUOTE=8shots]Nowhere in this thread did I talk about applying this information to any distance beyond 100m.

I'll give you that.  You hadn't yet, in this thread.
 
You must be having a weak moment!!!
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Direct Link To This Post Posted: January/08/2010 at 06:06
The proper reply Jon is.... Nuh-Uh!!! Laugh
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Direct Link To This Post Posted: January/10/2010 at 07:13
Ok, I made some pudding, now for the eating.
 
This Sat I managed to get to a longer range to try out the 400m stuff......well what happened????
 
These are all first targets and no repeats were shot. I made one attempt only.
 
First up I checked the 200m zero. The rifle was spot on. Whilst at the 200m mark I also focused the parallax setting on a 100 m distance and shot a grouping.
 
 
 
 
 
 
 
 
 
So far so good, both groups stayed under 3/4 MOA and would bring home the bacon.
 
At 400m :
 
 
 
Ta-daaa, both groups at 400m under 1MOA.
 
So yes, a consistant cheek weld that maintains the eye close to the optical path can  overcome parallax error.
 
I will however concede and agree with JonA (and this burns my >>>> to do this), that shooting accurately at the longer distances without being parallax free takes a lot of concentration and effort.
 


Edited by 8shots - January/10/2010 at 07:20
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Direct Link To This Post Posted: January/10/2010 at 08:07
8 Shot's Thanks for the additional info. I'm going to throw something out there for everybody to digest and I welcome any insight. Based on what I am seeing a scope that allows a generous amount of side to side eye position but without a parallax adjustment, while nice to use and possibly quicker to acquire targets with may not be in our best interest. Whereas one that is less forgiving will require a more proper cheek weld and shooting position and thus help reduce parallax error at longer ranges...
We measure it with a micrometer, mark it with a crayon, and cut it with a chainsaw.
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Direct Link To This Post Posted: January/10/2010 at 08:15
Biggreen, I will agree with your statement.
What determines that "forgiveness" is exit pupil size, which is determined by magnification and objective size.
The least "forgiving" scope will thus have the smaller objective. Then the trade-off begins such as brightness in fading light etc.....
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Direct Link To This Post Posted: January/10/2010 at 08:23
And unfortunately as with everything there are always tradeoffs. 
We measure it with a micrometer, mark it with a crayon, and cut it with a chainsaw.
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Direct Link To This Post Posted: January/10/2010 at 09:49
Thanks Wouter!  Good stuff as usual! 
 
Good shooting too, AS ALWAYS!
 
Gonna start calling you Steady Eddy!
 
If I had done that test the results would
have been a little more....umm...extreme! Embarrased
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Direct Link To This Post Posted: January/10/2010 at 21:37
Originally posted by 8shots 8shots wrote:

I will however concede and agree with JonA (and this burns my >>>> to do this), that shooting accurately at the longer distances without being parallax free takes a lot of concentration and effort.

Aww shucks, you make me blush.      Wink      Nice shooting.
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Direct Link To This Post Posted: January/14/2010 at 02:50
I've just got one question, and this is based on your mention of increased "concentration and effort"...Wink 
 
When you shot at 400yds with 100 yd parallax setting, did you just find a good full picture, aim, and shoot (the way the average joe who knows nothing about parallax would do), or did you take your time and center the error by moving your head up/down/left/right and finding the spot where the reticle travelled the same distance left/right/up/down from the bull??  Or..... did you back up on the stock until the edges got blurry, then center the now smaller picture in the eyepiece?? 
 
These are the two ways that I would use to lessen my error in a non adjustable scope, the first more accurate, the latter faster and easier....
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Direct Link To This Post Posted: January/14/2010 at 02:56
Originally posted by biggreen747 biggreen747 wrote:

8 Shot's Thanks for the additional info. I'm going to throw something out there for everybody to digest and I welcome any insight. Based on what I am seeing a scope that allows a generous amount of side to side eye position but without a parallax adjustment, while nice to use and possibly quicker to acquire targets with may not be in our best interest. Whereas one that is less forgiving will require a more proper cheek weld and shooting position and thus help reduce parallax error at longer ranges...
And this explains why the little Burris 4.5-14x32 is so sensitive to eye position on 14x.  Just holding it in my hand a local store, I couldn't keep it still enough to avoid blackness when the power was cranked up....
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Direct Link To This Post Posted: January/14/2010 at 04:10
Tbrake, the concentration and effort cam from using this system:
 
 take your time and center the error by moving your head up/down/left/right and finding the spot where the reticle travelled the same distance left/right/up/down from the bull
 
I tried backing off to have the edges blurred, but it seems more tricky, maybe because it forced my cheekweld into a position I was not comfortable with.
 
The reason for the scope being more sensitive at higher power to eye mnovement, is that as the power goes up, the exit pupil becomes smaller.
If you had a scope with a 1thou exit pupil, then parallax error would be largely eliminated. However, other problems would make the scope unusable.
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Direct Link To This Post Posted: January/16/2010 at 18:48
Originally posted by 8shots 8shots wrote:

Tbrake, the concentration and effort cam from using this system:
 
 take your time and center the error by moving your head up/down/left/right and finding the spot where the reticle travelled the same distance left/right/up/down from the bull
I don't have to tell you that your test has not proven anything for scopes without AO/side-focus Wink 
 
Your test has proven that you have good eyes, shooting skills, and a good understanding of parallax and how to correct for it.  Now set your scope to be parallax free at 100 meters, then hand it to someone who also has good shooting skills, but knows nothing about parallax or how to correct for it.  Have them shoot at 400 meters and see what happens.... This will represent the results of about 95% of the scope-buying public.
 
For example... my nonadjustable scopes that were factory set to be parallax free at 100 meters, had lots of parallax (8-10 inches of movement) when viewing the target at 600 meters. I could adjust most of this out with my adjustable scope to the point where they had little to no movement.  If I had handed my Mom (no clue about scope/parallax) both guns and had her shoot groups at 600 meters, what do you think would have happened??
 
In other words... I'm still convinced that adjustable parallax is always superior unless you intend to always shoot at one distance. 
 
I'm sure you also know that your head up/down/side/side method is pretty much impossible without having the gun benched on both ends.Big Smile
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Direct Link To This Post Posted: January/17/2010 at 09:39
all 8 is saying is that parallax isn't a big deal in the normal hunting shot. --regardless of distance.
 
off center parallax error from improper cheek weld isn't a problem when the eyeball is directly behind the optical center of the scope -- no matter who is shooting.
 
focusing parallax error is always there unless corrected by an ao (even if the eyeball is behind the optical axix) , and is a function of the objective diameter thus the smaller the objective the less parallax error.
 
higher magnifications -- magnify the error present depending on the amount there in the first place of the image projection behind the first set of lens.
 
in most variables below 15x the parallax error will be less then the cone of fire at distances beyond 300 yds.
 
trick with using a non ao scope, especially fixed power, is having a rifle/load combination that shoots as "flat" as possible to decrease the cone of fire (assuming its also a good grouper).
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Direct Link To This Post Posted: January/17/2010 at 18:55
Originally posted by Dale Clifford Dale Clifford wrote:

all 8 is saying is that parallax isn't a big deal in the normal hunting shot. --regardless of distance.

But that's not really what he showed.  If you need to shoot quickly, from a less than ideal field position, while choking down a case of buck fever (as is often the case when hunting), if you need to "take your time" and put forth "a lot of concentration and effort"--self imposed and in addition to everything else adding difficulty to the shot--you're not giving yourself the best chance for success.  
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Direct Link To This Post Posted: January/17/2010 at 19:43
to me it is --- the only thing that changes is the grouping of the intended point of impact.  which are well within the cone of fire. get a Pact timer and put it on yourself, whether under the pressure of competition or the hunt and try this with shooter ready positions standing.
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Direct Link To This Post Posted: January/17/2010 at 20:31
Again, "the only thing that changes is the grouping of the intended point of impact" could be stated as:

"the only thing that changes is the [Only thing that matters!]"

When the group moves from the vital zone to over the back of the animal or into its guts because you didn't take the time and go to the extreme effort required to center the reticle in the middle of the error zone as he described above, that's all that matters. 
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Direct Link To This Post Posted: January/17/2010 at 22:24
and again the kill zone is much larger than the parallax on any animal or human, even larger than the cone of fire in most cases. I found it interesting the 8s went to the trouble of illustrating it at distance. Parallax has its greatest problem in short range. This is seen almost every weekend in 3 guns matches. The parallax errors are there but less apparent because of the magnification of the optics used. (one of reasons to use a dot sight on the side of a higher variable.). and the low objective sizes. Use a 10 power on IPSC targets from 3 to 50 yards and the parallax is 4x his measurements, but will still be in the A zone. More errors (gut shots, etc) occur from hunters who have sighted in higher gain scopes at the highest power then returned them to the lowest for increased fov than errors from this parallax discussion.
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Direct Link To This Post Posted: January/18/2010 at 00:05
Originally posted by Dale Clifford Dale Clifford wrote:

and again the kill zone is much larger than the parallax on any animal or human, even larger than the cone of fire in most cases.

At close range.  This whole discussion began in a thread that was talking about error at 600 yds, which was observed to be 8"-10" through several scopes.  Expand your "cone of fire" with this additional "cone of error" and unless the vital zone you're going for is a chest shot on an elephant you had better do something to minimize it or not take the shot.

8s showed a good shooter who is cognizant of the error can take some time and deliberately apply specific additional techniques that will allow him to still make the shot (at 400 yds at least).  If he's in too big a hurry or forgets in the blur of pressure, or if a guy simply doesn't think parallax can be a problem and just points and shoots, he stands a good chance of missing his intended POI by a significant amount.  Yes, enough to completely miss an animal.

Quote Parallax has its greatest problem in short range.


Maybe in competition, where a tiny group isn't tiny enough if somebody else shoots a smaller one, or where targets are a certain number of MOA sized.  But in the real world the animals don't get smaller as they get closer to you.  Even a large angular (MOA) error at short range is less of a problem for hunting because the vital zone is that much bigger.  5 MOA off at 50 yds is no problem at all, 1 MOA off at 600 is unacceptable for the same sized target.
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