Sounds like you are fresh out of mountains and hill sides. We here in FL have the flat land problem also. You can pile up dirt to make a berm, if you have the free dirt. Another option is old used tires, stacked and filled with dirt, stack three then fill, repeat. Set them staggered and touching so bullets can't pass. Makes a fine bullet absorbent backstop.

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The 8'-10' tall wall process is fairly fast with a tractor and FEL with a bucket. Trick is to find a tire store that will give you the old tires and not have a prohibition against old tires on property. Stacking them full of dirt is not a big fire hazard.

Last edited by Rapier; 07/25/23.
“To expect defeat is nine-tenths of defeat itself. It becomes a self-fulfilling prophecy. It is best to plan for all eventualities then believe in success, and only cross the failure bridge if you come to it."
Francis Marion - The Swamp Fox