I don't own any rifles that have POI shift due to either barrel heat (cold bore) or from fouled condition. If I discover a rifle doing this, and the usual accuracy work doesn't change it, ie bedding, floating and pillaring, I don't keep them.
My rifles HAVE to put the first shot where I aim, I will never compromise on that, ever.
There are certain powders that DO show POI due to the temperature, but, if you avoid those, it will never rear it's head.
Cheers.
Could one reason for those "mysterious
misses" / "differences between the first
and the second shot" be that the
rifle system (rifle-barrel-scope-mounts-
rings-screws...) has been kept warm
in vehicle (offroad car/...) while travelling
to destination and the temperature
difference may have been over 40°C (100F)
between the first and the second shot ?
ref 1:
"in colder temperatures bullet speed
differences may vary between 5-20m/s
depending on the rifle and ammo
due to barrel heating"
ref 2:
"mysterious shots" right ~0,5 mrad !
ref 3:
"make sure you tighten your scope
properly for which you need strong
screws and rings designed for colder winter
temperatures"
ref 4:
"riflescope slipping occurs more often
in cold temperatures"