LOL, I guess you guys must have some sort of understanding. . . I'd be disappointed in my guests if they shot up something I asked them not to shoot at . . .
Anyway, that Smiley must be cold/hot-rolled sheet steel . . . almost anything "high velocity" will likely burn right through that stuff . . . I'd bet a Hornet would drive one through at close range . . .
T-1 is usually considered bare minimum for steel targets, and AR-500 is much better. Even with AR-500, those "notorious Scenars" (empty nose cone makes a shape charge?) still leave a pockmark, as will a .223 or similar at closer ranges, but the normal rifle rounds simply vaporize upon hitting it. Even a .338 Lapua does not permanently damage my 3/8" AR-500 targets from 500 or so on out. It knocks flakes of paint off the back, but the metal springs back with no real damage. After beating it awhile, it may take on a little bit of a bow or dish shape, but turning it around and shooting the back of it will bend it back again eventually.
Here are a few pieces of 3/8" thick AR-500 with multiple hits from 6.5-284, .308 and .300WinMag (210 Bergers) and no damage that a quick paint touch-up won't completely cure:
The center target is 3/4" piece of T-1 . . .
The bullets basically go to dust on the surface hardened plate, and our biggest fragments (within 1,000-1,100 yards) normally look like this:
Here is a piece of (softer) T-1, shot from the same range. You can see it's about "borderline" hardness, since some bullets left permanent craters while others just fragged:
All of these materials are substantially harder than cold-rolled or hot-rolled plate.