I have 60 acres out back and just made a portable backstop with (2) 3/4" backplates (170lbs each). Used an old county snowblade rack, extended the width so I could place (2) Bianchi AP-1 targets at the regulation 3' spacing and used railroad (black) stacking foam to elavate the targets to the 6' height.
It probably weighs around 500lbs and is moved with my tractor (forks). The AP-1 targets attach with springs loaded mounts at top...have an optional swing in place single target bracket.
I'm the only that will be shooting at it once it's put in place out back..(leads bullets only).