My original design, which has been changed, of course. No photos of the new style, but very similar. This one is too tall, and the 2x2's made it too flimsy, it would flop in the wind. My new design is shorter, 48", which puts the bullets lower into the berm for fewer ricochets, and more stability in the wind.
Basically, take a standard 2x4 stud and cut it in half for two 48" side rails. Cut two more pieces 21" and screw/nail to the side rails, for a 24"x24" frame. Cover this with a 24"x24" piece of cardboard. This is the upright frame. Three standard studs will make two of these.
Then build a base that the upright frame's legs will fit into and it's done. Make the legs of the base long enough for it to be stable in the wind.
The original 2x2 frame, which was too tall and floppy.
The old base, new style base fits 2x4 legs front to back, not sideways like this.
One of the new 2x4 upright frames against the old style 2x2. Much shorter and more stable, bullets hit lower on the berm too.
They work great! Carry the base and frame out to the berm, drop the base, jam the frame into it, and git after it. Wood is cheap and 2x4's can take a lot of stray hits before they croak. 2x2's and PVC will die very quickly from stray hits, ask me how I know.
I need to make a few new ones and take some photos of 'em. I've made some of these in the past and donated them to my gun club too.