Re: R-25 temperature variation
I read all the time about this and it baffles me. I have never seen this at all. In fact I have seen the opposite. I dont know if there are factors that we are not aware of that come into play such as load density, or high/low pressure loads, etc....but I have tested RL15, RL19 and RL25 in several different guns/calibers from 0 degrees to 80 degrees side by side leaving loads outside all night and regulating others in my house and warm vehicle and have always seen very consistent numbers (within 25-40 FPS) and in one comparison, the velocity increased a bit with the cold cartridges (????). I know of other that have performed similar comparisons with similar results.
On the other hand I found VVN540 to be fairly sensitive. I documented the spreads from -2 degrees, 55 degrees and 80 degrees incorporated this factor into my ballistic calculator. I set it up for a baseline. When I enter the current air temp, it adjusts my velocity accordingly (the beauty of developing your own software). The groups and suprisingly, my 300 yard zero did not change (the beauty of harmonics).
Regardless, I hear lot of comments about RL powders and they always seem to contradict.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.