nice article was intersting to read. i just bought a bushmaster ar15. xm15 e2s model. and i have shot about 200 steel tula through it and about 300 brass. i have mostly brass in my ammo stock but have about 60 steel tula. if a shtf scenario i really wouldnt care if i was using brass or steel. for range ill shoot the cheapest stuff i can get. if it ruins my rifle in a few years ill buy 2 more.