Why not set up a lawn sprinkler so it sprays in the bullet's path and compare group sizes to those fired in dry air? Seems that if you fired several groups you'd be guaranteed to hit a drop or two, not exactly controlled conditions I know but...
IIRC I read an article years ago by Col. Charles Askins in which he made a frame which held a number of very small dowel rods and shot through them at a target with several different rifles. Seems like the only thing that wasn't deflected a huge amount was a .458 Win Mag-and it was deflected some. I also recall watching a video of a guy firing a bench rest rifle in .50 BMG through a pile of brush at a target a few yards back; same result the monsterous slugs hit all over the target, most had keyholed to some degree. Neither Charlie's writings or videos of unknown origen should be taken as gospel of course, but I'll accept them on this one. If we are to err, let's do it on the side of caution.


'Four legs good, two legs baaaad."
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"Jimmy, some of it's magic,
Some of it's tragic,
But I had a good life all the way."
(Jimmy Buffett)

SotG