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Finding this hard to believe...

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Was out yesterday popping-off a few rounds to test the feel of the two-stage trigger in my latest Evil Black Rifle. My friend JR was there to test the zero on his rifle but he did not shoot because the sky was brightly overcast, and he said the bright but flat lighting would cause the bullets to impact an inch higher on a clear & sunny day. I find this hard to believe. I have to ask, "How does the bullet know it's traveling under a clear and sunny sky, versus an overcast sky that is still bright enough to trip the sensors of a chronograph? If the bullet is aware of its own existence, how can the lighting cause the bullet to gain altitude between the muzzle and the target?" JR is an old-schooler from Hartville, Missouri. He's just about 82, has his beliefs and stands by them. If he believes something, you'll be unable to dissuade him without regard as to how much evidence you have to show him he's wrong. Any truth to the bullet rising between the muzzle versus succumbing to the power of gravity because of the lighting conditions at the time of the bullet being fired?
 
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Short answer is yes. But not in the way you describe. The lighting does not affect the ballistics of the round but your perception of where the target is located.

Sunlight's influence on bullet impact

Sun angle makes target move?

A couple threads that describe it better than I ever could. The snipershide one has a Youtube video posted that shows a optic locked into a solid position with time lapse throughout the day. as the angle of the sun changes and brightness ebbs and flows with clouds you will actually see how the targets seems to move around slightly. This would cause you to have a different POA depending on lighting conditions and angle of light which will affect the POI. You can research Snell's Law.

Hope it makes sense because the first time I heard this i thought "thats hogwash", but after researching the physics of light waves, atmospherics, and seeing that video I can definitely see how zeroing on a overcast day could cause your friends rounds to impact high if he is shooting on a clear bright day.

posted a couple videos from the threads in case folks want to see them.
 
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nvshooter
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Thank you for the reply. I have yet to read it (just got home from a very long trip), but the reference to shadows moving across the target makes sense. I shall read what you dug-up later today. Right now, I need sleep-- and very badly...
 
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I used to go out to Ben Avery and shoot my 45-70 at silhouette targets at distance(600+). There were days when you needed two spotters one on each side of you to get accurate corrections. We all know that the 45-70 arcs a bit at distance. So that was part of it. I never realized the sun played such a big part of the equation. thanks for posting this
 
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nvshooter
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BigDaddyDMD, Great explanation. I'm getting absolutely nothing out of that string of characters. Does not turn blue when I place my cursor on it...
 
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BigDaddyDMD, Great explanation.
Thanks, but I am just parroting information that those smarter and more experienced than I have shared in the past. The more I learn about long range precision shooting the more I realize I don't know squat. It is a terrible rabbit hole to fall into. (Not really. I enjoy the crap out of it). Went out yesterday and getting first round cold bore hits on 18" steel at 1000yd made my day. Was feeling pretty good until the 1375 yd kicked my butt. Just couldn't get a read on the wind and myself and my spotter were having trouble seeing splash to make corrections)
 

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