sun on rifle changing poi at 950 yards.

[30-06 boy]

this past season i learned a lot.my rifle is a savage 110fp in 300wm,nikon buckmaster 6-18-40,walnut benchrest stock.at first light my brother and i set up our hand made shooting benchand rifle.did some glassing and decided to shoot a few sighters at a big rock at 950.18 degrees slight crosswind to right.put the clicks on the scope for elevation.boom....then a puff of dust off the rock.moved windage 1 moa to left.boom...jackpot.saw nothing all day to shoot at.at 4pm we decided to pack it in.temp is now 35 degrees.but the sun has been on rifles right side since about 8;30 am.decided to try the rock again.didnt take clicks off gun from morning.boom...no dust??shot went about 3 feet right and 2 feet high.coulnt figure it out untill i thought about the sun on the gun.i'm sure thats what did it.what do you guys think?

 

[Michael Eichele]

I suppose sun heating one side more than the other MAY cause a shift. More than likely it was also differant lighting conditions. If you hit it at or before sun up and then mid day, shot again, this can easily account for SOME your miss. Add some mirage in the mix, warmer loads, and well, thats why concistently hitting small targets at 1K is not easy! You must also concider the cold bore shot. All these things could have easily added up to make you miss that much.

A shooter must note whether he sighted in bright blue conditions or grey and cloudy conditions and change his settings accordingly. Differant lighting conditions do differant things. Practice, practice, practice.

 

[Michael Eichele]

Also, you didnt mention what the wind was doing during the afternoon attempt.

 

[arthurj]

What direction was your target: N, S, E, W ? The different angle of the sun relative to your target and your scope might have caused this change. Say your target was due South, at 8:30am, with the sun at your 9:00 East. By 4:30 the sun has moved to your 3:00 west, this will cause you to view the target differently. It may appear to be to the right, when it is in the exact same place that it was at 8:30 am. The different angle of incidence of the light coming from your target causes you to see it in a different position than it actually is. This may account for the horizontal error. Depending on the direction of your target, this could also account for the vertical error. The slight increase in temp had some effect on that vertical though.