Toro,
I built a lightweight version of that type for my daughter to use with her 22 rimfire when she was young. I used 3/16th diamond plate I had as scrap from another project, (I put the diamonds on the outside) and it lasted her 4 years and about 250K rounds until she graduated to centerfire. (she shoots service rifle matches now) After all those rounds, there was a slight bulge in the main impact area and she always shot at 50 yards. I'm thinking 1/4" plate would have held up a little better.
The indoor range that I used to use a lot had a 1" plate on a 30 degree angle deflecting the bullets into a sand pit. That held up for 40+ years of pistol rounds however at each port there was a slight indentation. They were replacing the plates so to see what would happen, they tried centerfire rifles, a 223 AR, 308 FN/FAL and 30-'06 Garand. All three went right through the plate at 75 feet. I would be cautious when you try yours out.
Tom