I would have to agree with your thoughts about the wind and the barrel heat. However, this still appears to be a pretty tight group. What yardage were these shots fired from? They all appear to be in the kill zone.
I am assuming all of your cleaning or shot routines were the same each time? I ask, because when I really try and get an accurate group, I only shoot once then do a complete clean and let the barrel rest for 15 minutes or so then load and fire again. I do this routine three to five times to figure out what my groups are doing. I figure I will only get one shot in the woods, so I better make sure all the first shots are the same and accurate out of clean and cool barrel. I also bring a couple different guns to the range with me knowing I have to do something while the barrel of the first gun is cooling off.