I have to recommend http://www.shooterselement.com Taylor makes his targets out of AR500 and they take all kinds of punishment. He's in the Phoenix area but he'll ship for free on orders of $80 or more. He's a vendor on a Arizona gun forum I help moderate.
Just a dog chauffeur that used to hold the dumb end of the leash.
I've been pleased with the RSR ready to ship A/B target. It is a robust setup and the steel tonality is nice and loud.
https://www.rsrsteeltargets.com/product/000-RST.html
I made hundreds of steel targets before retiring (welding teacher). I am fortunate enough to live about 100 miles from one of the world's largest manufacturers of haul truck beds for mining. I have used SSAB/Hardox by the tons. There is a difference between hardness and toughness.
"It’s not that hard to make hard plate. But it’s really tough to keep it tough through the process." That is a quote from SSAB's website. I still have a couple of tons of AR440 Hardox 3/8" thick. It tested at 485 Brinell so I keep it around. FWIW, I have seen 500AR from other sources that tested as low as 475 Brinell. I suppose that is neither here nor there. As far as M193 ammo, just don't use it on steel plate, problem solved. The amount of heat generated when striking a plate will really put the plate's ability to resist cratering to the test. Repeated shooting can also limit the life before the plate loses the ability to resist deformation in the form of cupping. Remember to turn the plate around frequently. Short answer, if you don't want to take chances with your dollars, go with one of the well known makers like MGM, Action Target, etc.
Sorry for the necro post, but does anyone have experience with the Sportsman T-Post targets from MGM? My club stipulates that steel targets must be swinging.