Cold bore is largely a myth. Clean bore, of course that is a thing, follow up shots are in a different condition.
If cold bore is mechanical, it is the rifle getting jostled so that something gets out of place and then upon the first shot it returns to its neutral position. It could be bedding, scope movement, barrel movement relative to stock if it touches, internals of the scope moving, etc.
But, the common element is always the human that is not well practiced and did not build a solid position for the first shot.
Once a shooter settles in, it is much easier to shoot small groups.
Test it by doing build and break practice. Pick up right rifle, do the Hokey Pokey, reset the rifle to low power, load the magazine again, then try to build the same position.
I guarantee that groups shot during build and break practice will not look like groups when you get settled in and fire them without breaking position.
After firing, there is often slack taken out of the human/rifle connection, fill in bags settle, eyes blink less, the rifle butt slips to a position it rests more easily in, etc.