Yes, the Westinghouse MN is made out of crappy American steel. The French made MN are made out of blue cheese. The Finns used what they could find, like Codfish for the stocks and also made barrels out of frozen snakes. I have one made in 1898 for the czar then converted by the Finns into a M27. It has never been shot. The other day I picked it up, and it crumbled to snake dust. Finnish barrel. Been a heat treating tool steel and others for a long time. Every batch of steel made is different than any other batch ever made and you would have had to have been there to know what is in it, or, have some really good lab. Voids and chunks in MN steel? Yeah, that sounds like them being economical. The Chinese made some out of noodles and they held up pretty good. Many countries have made them and they all use just what they had laying about, I mean just because it has the similar ballistics to a 30-06 doesn't mean it has to hold that pressure. All of the dead Russians in WW1 and WW2 died because their guns blew up. Why did they keep making them? Oh, over population. The ones imported into the USA have not ever been shot, not even once, or, they would have blown up. Yes, I know steel.