I can't say that I've had this problem with my Leupolds, are you sure it's not just the temperature change affecting your ammo thats shifting your zero? A 30 degree F change shifts my POI about 1 MOA. If you have ruled this out, look at your mounting system, if you've got some lower end scope mounts (made of cheaper, stamped metal) they could be more vulnerable to heating or cooling shifting your POI. I use Badger Ordnance mounts, they weigh a ton, but can take whatever you throw at them.
------------------
Cry "Havoc!" and let slip the dogs of war.
