Re: 1000Y challenge! Test your 1st shot hit capabillity.
If one ever watches a 1000-yard scope sight match where folks lay down and shoot prone then keep track of where their first sighter shot goes relative to the target's 10-inch X ring, here's what their notes will say. Note that this applies to a wide range of atmospheric conditions; temperature, altitude, and wind speed/direction.
At 1000 yards, about 5 to 7 percent of the top classified shooters will put their first shot in that X ring. In the USA as well as other countries using the same target for their long range matches, those top classified competitors represent about 5% of all competitors. All of which means that 3 or 4 out of a thousand competitors will put their first bullet someplace in that 10 inch circle. I doubt the long range hunters on this planet will do any better.
Biggest error is in correcting for wind. It's impossible to accurately determine the wind speed and direction for every yard of range between muzzle and target. So it's only an educated guess to predict what the wind drift will be at long range for a given bullet at a given muzzle velocity. The higher the average wind speed is the harder it gets. And it will usually change a little bit between the time the bullet left the barrel and when it reaches the target.
Regarding the repeatable accuracy of shots from only cold bores, if the atmospheric conditions remained constant, all the shots from cold bores would equal the accuracy of what several shots from hot bores would produce. Those top ranked long range competitors mentioned above use barrels that are properly stress relieved and fitted to receivers such that they don't change impact significantly as the barrel heats up. They'll start with a cold barrel then shoot 15 to 30 shots and no corrections are needed for the barrel heating up; excellent accuracy's maintained.