Up till this weekend when I went to the range it had been cool, but this weekend it got up to 81°. And I found something about the polymer upper, after shooting two (25) clips I put the weapon down on the tail gate to reload both clips. And as I said it was 81° and the sun was good and warm, so when I started shooting again it was shooting low and to the right. And I had several FTE. I noticed that the side of the weapon that was up when I laid it down was very warm and the side that was down was cool. After the first clip it started shooting closer and closer to dead on again, and could not tell much diffence in the temp of the weapon form side to side. I then laid the weapon down but this time on the other side, and sure enough it started shooting low and to the left. Seems that the sun would get one side hotter and the polymer would warp and that would move the scope to make it shoot off.
So keeping that in mind anytime I am not shooting I will keep this weapon in the shade.