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Discussion Starter #1
OK, I am trying to remember something from my highpower rifle days, but am having a case of CRS.;) Assume I am shooting a black bullseye using a receiver sight and a post front sight. I am zero'ed for a dull overcast day. What is the effect of the POI with the same sight picture if the sun comes out, shining on the target? Does it make me shoot lower or higher. I remember the adage "light up, sights up" but I cant remember exactly what it means. (really BAD case of CRS!!:eek: ) HELP!!
 

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Lights up - sights up! I shoot a lot of high power and when the suns up you get a little glare off the top of the front sight which obscures the bull. You tend to aim lower on bright days:)
 

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Sun acts like wind..............Was shooting well actually trying out

for the State Pistol Team many years back, and the emphasis was definitely on the "trying". The range was oriented to where the sun was traversing right to left. At the long line (50 yds) and the short line too (25), I had to click toward the sun. By illuminating the bull on one side more than the other (we are talking subtle shades) it effectively would reduce the apparent size by fading out the right portion therefore causing me to hold left to center my 6 o'clock hold (irons). The human eye can discern minute variations of shading and in this situation, do it subconsciously as our focus is on the front sight. Hope this makes some sense.

Do understand that at that distance, it was only a couple of clicks. I doubt if those several clicks on the first couple of targets made that much difference to cause not being chosen as I was very new to the game and just trying to find my way to the line w/o getting lost.

Now, I have a question for tbs: Is not your front sight hooded? Or does enough light sneak in to cause problems?
 

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I shoot service rifle class and John Garand match's, so no hooded front sight. If I was shooting match rifle class then I would definately have hooded front and that would eleviate the problem glare.
 

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Discussion Starter #6
Thanks, TinMan, that was exactly what I was looking for:) Here it is: . You're right about the elevation changes. That happens when
the light intensity goes from low to high and the shooter's eye iris
gets smaller. When that happens, the aiming bull appears larger and
the front sight post will still appear the same size, but when touching
the bottom of the apparently larger bullseye, the shots will go low.
In darker (dimmer?) light, the eye's iris gets larger and the bullseye
appears smaller causing the front sight post to be closer to the center
of the bullseye; the shots go higher. The `light's up; sight's up'
rule of thumb is very correct for post front sights whether they are
hooded or not. Typical correction varies from a quarter to almost a
full minute elevation change depending on the person's eyes and light
condition changes as well as atmospheric conditions. When aperture
front sights are used, this doesn't apply; the bullseye centers in the
round aperture regardless of how big it appears, but the aperture size
might need to be changed to allow a better sight picture.
 
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