We have several Steel Targets for our Steel Challenge Pistol Match. The targets are all 1/2" thick. Some are mild steel, and some AR500. All are holding up fine.
Most of the Frame parts are 1-1/2" or 2" angle iron 1/4" thick.
For hanging targets a piece of square tubing weldeed on the top of the back side will work well to hang it by a chain. This angles the bottom back. It also is easier to repair a damaged chain. We have a 1" and a 1-1/2" thick hanging target at 100 yards. You would never believe how badly shot up they get. The 1" is a 12" X 12" plate. It has about 25% of the bottom shot away. The 1-1/2" plate is a 12" round Plate. It looks like a coral sponge, wall to wall deep craters.
We have as couple silhouettes hanging at our long range impact berm. One is 1" AR400 armor plate, and the other is 1/2" mild steel with a 1" Strike Plate added in the center. They are normally shot from 600 back to 800 yards. We also have a 1/2" AR500 sighter plate.
We have one hickie on the 1" AR400 Silhouette. A 15 year old girl got on the wrong silhouette with a 50 BMG Bolt Gun shooting AP. It did not go through from 600 yards, but it left a mark. The 1/2" silhouette is the junk target for things that might damage the Good AR400 target. It is needing rebuilt or replaced again. It takes a beating from 300 Magnums, 338 Lapuas, and 50 BMG's.
Bob