NRA Action Pistol Plates are just the thing. 8in. dia. either 1/4 or 3/8 thickness. If you use mild steel 3/8 is much better. A really hard steel can be 1/4. Lead bullets only in pistol cal. Do not shoot these with jacketed ammo,at best you'll punch holes in the plates,at worst something will bounce back & you may have to attend a funeral. (your own)
Contact NRA Competition Dept. They should have drawings you can use to build a set of plates. These reset with a rope & we have had ours for many years.
As to distance, no closer than 10 yd. As far as 25 yd. is what we use. Although that might be 35 yd. I'm not sure. I didn't build that set-up but I do love to shoot it. Check with the NRA, there is somebody there can fix you up.
Hope this was at least some help. :-)