If you're only using it for pistol, what ammo are you going to use? Frangible? You should be alright on mild steel around 3/8 - 1/2" for light pistol rounds with frangible ammo. My steel plate at 900 is a 10"x10" mild steel plate 1" thick and it holds up just fine to 338 Lapua, 7mm Rem Mag, and of course .223 doesn't even phase it. Hell, .223 barely removes the paint at 900.