Don't so cheap on the steel. Navy Joe advised you correctly. Your target need to stay FLAT and not dent or cup to prevent lead coming right back at you. Good steel choices of 9mm and .40 cal would be AR-400, AR-500 and TIA. Mounting is also very important. I do not weld targets to chain as they break. I drill the targets on each side, use hardened bolts with square washers and attach the 3/8" chain to the back side. This allows the target face to hang with the bottom slanted towards the back, directing hits into the ground. I hang the steel off fence tee-post that have hooks bolted onto them. The swingers are free to move and adsorb the bullet impact. I cut targets in many shapes - animals, round, square & triangles. My set has been shot at a bunch and shows very little use after 20 years. Best of luck, Dan