やみよにてっぽう
aimless attempt; shot in the dark
Noun
闇夜やみよに鉄砲てっぽうじゃあるまいし、そんな場当ばあたり的てきなやり方かたでうまくいくとは思おもえないよ。
That's just a shot in the dark. How do you think you'll succeed by just acting on the spur of the moment like that?