We've had a few discussions about the effect of rain drops on supersonic bullets, over the 15+ years that I've been around here. I did some
math in one of them.
Some disagreed with some of my assumptions, but I believe we all figured it was roughly the correct ballpark.
My conclusion (assuming constant velocity):
A .308" diameter bullet traveling at 2,100 fps to a 100 yard target has just a 0.0139% (1:7175) chance of hitting a rain drop.
The smaller the bullet, the better the odds. [of no impact]
The faster the bullet, the better the odds. [of no impact]
A .224" bullet traveling at 3,900 fps has only a 0.0054% (1:18,323) chance of hitting a rain drop in a two-inches-per-hour rain storm.
From a claimed meteorologist:
(...) the impact of a 1gr drop of water on a 165gr bullet will be negligible (something in the range of 1/10,000th of one MOA if my division serves me right) (...)
Your odds of measurable bullet deflection due to rain is roughly the same as the odds your bullet will be struck by lightning in midair.
But in the subsonic realm, the "negligible impact on the bullet," probably goes out the window. So that sounds like the answer, right?
The thing is, you have to
hit a rain drop for it to matter, and those are long odds.
.