I think its safe to say that all American Milsurp ammo is non-corrosive
It is not.
There is still chlorate primed USGI .30-06 and .45 ACP from WWII and Korea available here and there. Fortunately, the US Army kept good records and the time and even the lot number of the changeover is available.
I would play it safe and wet clean all the foreign stuff.
I bought a .223 once. It was dirty but apparently sound and the price was right. I later found that it had probably been left dirty to conceal a dark bore. So SOMEBODY made corrosive 5.56. A new barrel kind of wiped out the good deal.