I was target practicing on public land behind a dam at a Lake, so I was shooting into the dam hill with a .22

I was able to hear some of the shots ricochet off the ground, which really bothered me so I cut my practice session short. I don't think I've ever had that problem before... Of course, with the big guns, it's not a problem.

What would you recommend for a back stop that's portable for a 22? I was thinking maybe just a car tire,... think that would be ok? Or any other ideas??