It also depends on how they "hang" folks, if they "hang" at all.
I have three AR500 steel targets 3/8 ". One is 8", one is 6", and one is 4". They are rated for modern rifle, jacketed bullets, and they work fine for those. They also work very well for lead round balls and conicals. In fact all lead or lead alloy only knocks the paint off their surface. So for BP shooting, they should last pretty much longer than I will last.
Anyway...
IF they are bolted to a 2x4 or 4x4, they only make a sort of "donk" sound.
If they are suspended from chains, or from an actual steel plate holder
https://www.sportsmansguide.com/productlist?k=steel+plate+ they ring much better, since the steel is able to vibrate. I just use cheap, small C-clamps to hook the chains onto and clamp on a target backing which lets the plate hang about 2" in front of the target backing at the range, and for where the plate attaches, I use cheap aluminum "carabiners" made for holding car keys (not actual climbing carabiners). With the all lead or lead alloy bullets there's no worries, but..., if you also try jacketed bullets, if you hit high on the plates, near the carabiners, after a while, they get damaged by the splattering copper from the jackets, and fail. Pretty cheap replacement though. They ring fine
The BEST ring I've seen is when steel wire from a coat hanger is used, on a plate with a single hang-point. You need a backstop close to such a plate, as a hit will spin it and swing it something fierce, but the small amount of surface contact from the coat hanger wire gives the most vibration so the most sound. BUT it's also fragile and easy for the bullet splatter to cut that wire.
What does NOT work...is cast iron pot lids, or a cast iron, round griddle.
https://www.webstaurantstore.com/lo...iron-fajita-skillet-with-handle/530L6OG3.html My .530 patched ball fired with 70 grains of 3Fg will zip right through one of those hanging at 50 yards.
Not a cheap alternative to proper steel.
LD