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Ah... but the KEY part is, if you don't KNOW... ASSUME it's not safe to use smokeless and you'll be fine.

As for rusting in welds... the damn barrels are so thin and you cannot inspect the welds...

I don't think there is any benefit to pattern welded steel today. It's done for appearance sake.

While wikipedia is hardly the last word on such issues, after reading what they have on pattern...