Any decent operator can scrape up enough material for a berm.
My first berm was about 6 feet tall and 10 feet wide. It worked fine for decades.
My current berm is about 8 feet tall and 25 feet wide. A true ricochet is not much of a danger, the bullet bleeds energy rapidly.
The States range down the road is only about 20 feet high, but that takes a lot of material.
A modest berm is fine if you exercise good judgement.
