I used to hang 1/2" cold rolled for muzzleloader, 22 LR
and handgun with lead or soft nose. They worked okay with 3030 and 3006 but 3/4" to 1" cold rolled lasted lots longer with the rifles.
223 wore em out and holed em durn quick.
AR 500 or equivalent armor steel plate lasts the longest. But if you restrict yourself to lead or lower velocity Jacketed soft nose handgun the cold rolled was fine.
I just went to the steel shop, had em plasma cut holes in scrap chunks and hung em on chain from a steel pipe supported by a couple wood posts.
We hung them at 50, 100 and 300 yards. Natch, the 300 yard ones lasted longest even with the 223 and 3006 and not entirely because the long range ment more misses!