Not transportable, But you may want to rent or Have a Friend use a Bobcat to push up a nice mound of Dirt to make a Backstop. Its fairly easy work and could be done in a few hours, Just depends on how good you want it to look. But if it stops a Bullet, It works.
I have also saw a friend used Thick Steel to make his own Bullet Stop. He lives in a Close community and wielded together a Backstop with a Sandpit in the bottom to catch the Bullet's. It was angled to make the Bullet go to the Sand. Still works to this day. It weigh's a Ton though, But is very very durable. Never a problem with it.
I know they are not portable or moveable, But if you want anymore info on either one, Id be glad to get the specifics for you.