They used steel because it didn't flatten out and lose velocity when it hit someone. It would penetrate a body and continue on to do more damage to the next rank.
I use Lee drum dispenser with Black MZ. I use different brands of brass to differentiate between rifles loads, pistol loads and smokeless. My shotgun loads use Magtech brass or various paper hulls for black powder and plastic for smokeless.
I lived around there for about 3 years between 6 and 9. I lived in Goldfield, Lathrop Wells (now Amargosa Valley), Lida, and Indian Spings. It was interesting because they were still doing the A-Bomb testing in the area of Lathrop Wells and when I lived in Indian Springs the Thunderbirds practiced there
I'm like Phantom, I have to reload cause I shoot Black Powder as well. I use a Lee-Load-All for my paper shells and an old Lee Loader for my brass shells.