I do actually have some advice for you though.
Rent, buy, or borrow a Bobcat/skid steer and go to town. After my dad retired he rented one multiple times (he finally bought one) and built or ripped down anything he wanted. I'd call an 8' berm plenty good myself. Doesn't take a lot dirt to stop a bullet. Making the berm in a U shape could be nice for multiple target placements.
Travis
