There is no question that environment can have some adverse affects on internal ballistics. Last year I had an experience with water in the barrel that I posted on and this year, I had another strange thing happen that has not been talked about yet. I had a load with N570 behind a 225 grain ELDM that I ran a ladder test on at summertime temps (I think mid 70 degrees)? I chose a load that shot very well that was 3 grains less than my max load fired. This fall I fired 2 rounds at 40 degrees while hunting. The rounds had been in the magazine overnight in camp (not heated) I blew the primers on both rounds!!! No water in the barrel this time, but could have had SOME condensation?? The only known difference was the temp, which doesn't seem that extreme to me! I have been reloading for 50 years, and both of these things were new to me. At least to this extreme!.....Rich