Never.
Or maybe not, once my friend shot his .22 Cutlass at the earth berm at 25 M, but the pellet came strait back and hit the back wall in our old shot shed.
Very easy to hear as the back and side walls are corrugated metal, we was sitting in the R side of the shed opening, so it passed in the empty half to our left.
I still do not get how a 45 - 55 degree slanted fairly loose sand berm can return a shot like that, okay there are stones in the sand there too, mostly the size of 2 - 5 dices, but not really many of them.
And sice then we have shot to there a ton, and at least me targeting little stones, and at best i crack the stone if it is flint or i get the pewwww of the ricochet as it zoom off i assume up and further out back if i nick one of the larger ones.