Re: sun on rifle changing poi at 950 yards.
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.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.