My experience is that the temperature of the rifle does affect velocity. I have tested ammo both ways, by heating.cooling the ammo only, and by firing in outdoor conditions from below zero to 100F, with the ammo often heated a little more by "greenhousing" it in a clear plastic bag. Sometimes frozen ammo works about like it does in actual cold, but more often it doesn't.
This would require quite a bit of explanation before I'd buy it. The working theory is that powder burns differently depending on its start temperature. Possibly the primer explodes differently too. If changing the temp of the rifle chamber or barrel mattered, an entirely new physical theory of what's happening would be required and not much is coming to mind. Maybe the bore contracting in the cold?!? I did a little math on that, and I believe going from the hottest to the coldest possible "cold bore" barrel temp only changes the bore diameter a couple ten thousandths, so that's hard to believe.
I'm not saying it's not interesting, but absent a physical theory of what's going on I suspect error/testing difficulties.
Maybe poster denton will chime in on this topic. He has studied the effect of barrel temperature.
