Apparently the speed of sound depends mostly on temperature and not much on pressure or altitude.
https://en.m.wikipedia.org/wiki/Speed_of_sound
At 20C it is 1125 f/s
At 0C it is 1086 f/s and “Standard Velocity” ammo might creep over that.
I understand there are special low temperature ammo for biathlon to avoid the bullet going across the speed of sound and becoming unstable.
I wonder if this happens more in the autumn and winter. People whi shoot rabbits down in the McKenzie and Central might know more from experience …
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