855 ammo at 100 yards is going to tear up most steel. The steel core also is a huge spark hazard.

All I can recommend is MGM ABC Zone steel that hangs at an angle. It is still going to get chewed up but not as much as something that sits square.

Once the steel is pitted, chances of frag coming back at you, even at >100 yards, goes way up.

In other words, get good steel and use different ammo. Even Smoky The Bear will thank you.