Where to buy steel?

Big dog..I have many pieces of steel all are stated as AR500 all shot with the same bullets/guns and the big dog plate has no dents or poc marks...either it's of a higher quality or the others are less..

Go big dog steel and don't look back
 
I just ordered 4 post brackets and a 5" plate from https://www.shootsteel.com/ last sunday and had my steel by thursday with the best packaging I could ever think of for steel. I was very worried about the package being damaged and the steel falling out on the trip. I was very pleased with them so I went ahead and ordered 3 more plates!
 
I just pick up 1/2" steel plates cut in various shapes at the local scrap yard. Typically sold by the pound, you can get stuff for very cheap. I got 12" and 16" circles of 1/2" plate for like 5 dollars. Spray paint em white, drill a few holes in them for mounting, and you are good to go for a long time. When you have blown them to all hell, sell them back to the scrap yard for credit and grab some more. Works just as well as any of the fancy steel plates you can buy.