300/400 low grade series SS, same stuff your cheap pots and pans bought from Walmart.
Aftermarket use better grades, hell I've still got some aftermarket in the white carbon barrels that have been sitting for years for projects with no rust.
Who isn’t using 400 series SS?
Barrels and receivers are 400 series, who knows what they use for the smaller cast and MIM stainless pieces, but I would guess the cheapest #### possible.
HMM �� WHAT u meaning ? - sayin ? RJ