Making some targets for a friends range. The first ones I made were 1/4 inch plate. They worked well for handgun ammo... until he decided to shoot it with .223. So now I am upping it to 1/2 thick and am using a better hanging system for them.
Btw, some 5.56/.223 , depending on the load, can penetrate that. I've got some tracers that won't but I bet would be a helluva show once that bounced off it if less than 100 yards.