I think you possibly mean resetting plates. I think there are a couple of talented machinists/inventers on THR. jmorris comes to mind but to get plans one may be better off searching the web.
"Swingers" reset automatically. (My bad)
I have done what troy fairweather has done, cutting plow edges, actually called "cutting edges" welding the 5-6 inch piece to a rod with a piece of pipe welded parallel to the opposite end of the cutting edge piece. Weld piece of cutting edge to the vertical rod on the concave side of cutting edge. This will be the back side of the target.Shooting at the convex side of the cutting edge minimizes ricochets.
The pipe opposite of your target serves as a pivot point for swinging that a piece of pipe or heavy rod pushed through mounted between two 2 A-frames can swing on. clear as mud, huh? (Crude grade school drawing included.)
View attachment 831523
These are heavy targets. Big bores will make 'em swing.(i,e. 460 S&W)
After making this set up I later discovered that a frame holding your steel swinging targets that is light and has skis mounted under the "A"-frames allowing rearward movement, made more sense to absorb the bullet energy. YMMV.
Then one of our two machinist sons made me these........some kind of heat treatment and coating.....
View attachment 831522
Garage door panels are 2 feet to give one an idea of the targets size. 8, 6, & 4 inch circles.
One can see that I destroyed the middle sized target......
After that I decided not to use magnum and rifle rounds at these purty targets.
Be safe!!!