I only have two backstops set up for the time being. One is 100yds and the other is 500yds.
Here is a pic of the 500yd setup;
I do a lot of my load development at 100yds and it looks just like the 500yd backstop (no gong) but I have 1/4" steel lagged to the back of the railroad ties. That, plus a piece of plywood in front, helps to keep it firm and locked together. They last a pretty good while but will eventually get shot out if you don't shuffle the target around.
My gong is set up on landscape timbers (< $5.00 ea.) buried 2 ft. deep. I'm not sure what this metal is from but I found it here on the property when I moved here. I welded two pieces of chain and hung it on hooks. I had to weld a couple of metal plates to stop the bullets. The .300WinMag (180gn) and 6.5-284 (120gn) were zipping through it like a drill press. That was Ballistic Tips too.
Hope this gives you some ideas. JohnnyK.