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group shifting question

 
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  #8  
Old 01-04-2010, 03:46 PM
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Re: group shifting question

Quote:
Originally Posted by Michael Eichele View Post
+2 on the lighting.

Pay attention as to where the sun is when you sight in and then where it is when your group seems to shift.

I have found that when I sight in on extremely overcast days or when the sun is at 12 oclock and another day the sun is at 3 oclock, my POI is right. When it is at 9 oclock, the POI is left. I noticed this first in archery. Every time the sun was left, my groups were left. Every time the sun was centered, so were my groups. When it was right so were my groups. All other seriousd outdoor tournament archers noted the same thing.

I dont know the science behind it but know it is a proven fact that differing lighting conditions affect your perception of target to scope alignment.
Michael.....VERY interesting info. I too have experienced this phenomenon but never could figure out what was causing it? I wonder how many rifles, scopes etc. have been messed with for no reason? Next time I shoot, I'm going to pay attention to light angle! I hope others will also and post their findings.....Rich
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  #9  
Old 01-04-2010, 04:06 PM
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Re: group shifting question

I must be a lucky one, I don't think that I have ever experienced this type of problem. It could be that do to poor on no form it don't notice it!

Tank
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  #10  
Old 01-05-2010, 05:51 PM
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Re: group shifting question

Same things happens to to me occasionally. Usually cant is my problem.
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  #11  
Old 01-05-2010, 06:34 PM
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Re: group shifting question

Quote:
Originally Posted by Limbic View Post
Same things happens to to me occasionally. Usually cant is my problem.

That is something I have figured out now that I have an anti cant device. Its amazing how far off the shoot can be if it is not lined up the same every time.

Tank
__________________
Matthew 7:13-14
"Enter through the narrow gate. For wide is the gate and broad is the road that leads to destruction, and many enter through it. [14] But small is the gate and narrow the road that leads to life, and only a few find it.

If you find your self in a fair fight, your tactics suck!- Marine 1st Sergeant Jim Ryfinger

Friends don't let friends develop canonitis!-chucknbach

arguing over the internet is like the special Olympics....even if you win, you are still...special!
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  #12  
Old 01-05-2010, 08:26 PM
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Join Date: Dec 2008
Location: Cranbrook, BC, Canada
Posts: 155
Re: group shifting question

I suspect different shooting glasses will also change POI. I need glasses to drive, but rarely use them elsewhere, If I use my Rx glasses shooting my poi moves differently in each of my scopes. I didn't think of light conditions but it seems plausible.
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  #13  
Old 01-16-2010, 11:59 PM
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Join Date: Mar 2008
Posts: 531
Re: group shifting question

I adjusted my cheek piece (higher) and made sure it was aligned with bore. I am hoping this could have been the problem. I went to the range today and only had a little bit of t ime so i shot steel from 400- 875. The zero was right where i left it last time. i shot back and forth at all yardages in between and I moved the windage 3 over at 600 yards and it hit right where it should have. i moved it back and again, it did what it was supposed to. i re-zeroed and put two bullets right together at 875 right near the center of the steel. I didnt get a chance to box test today, but still plan on it later. however what i did tells me it shouldnt be the scope. all was well today, and i hope the next time i go there arent any issues. thanks for the help and replies.

also, as far as i can remember this problem has only happened at 100 yds. I actually only reset the zero for windage once, based on a session and the next time i shot with some distance i had to move it back? i could be wrong on this, but to the best of memory. anyway, thanks again.
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  #14  
Old 01-17-2010, 01:46 PM
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Location: Fairfax County, Va
Posts: 683
Re: group shifting question

If your parallax is out and you have a slightly different cheek weld that can do you in.
Try this, with you rifle in a solid rest, look through the scope and move your head around slightly, if the cross hairs appear to move on the target the you need to adjust your parallax, IF your scope is adjustable, until the cross hairs (reticle) do not move when your head does.
This could be why your POI changes from session to session if your cheek weld varies from session to session but stays constant during a single session.
Just another possibility.
Dave
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