Gunpowder ages and as it ages it gives off NOx vapors, some of which convert to nitric acid gas. That nitric acid gas ruins brass, causes pin holes, green corrosion, body splits.
A reasonable shelf life for gunpowder is 20 years with double based and 45 years with single based. Exposure to constant temperatures above 90 F, above 100 F, reduce the lifetime of gunpowder to months, weeks. Combustion pressures are raised to unsafe levels in ammunition stored under long term hot conditions.
Suspect gunpowder is tested in 150 F ovens, if it fumes within 30 days it is considered unsafe for continued storage.
So, I would dump the powder out of those cases and examine the cases. If there is no evidence of pin hole corrosion, green corrosion inside the cases or on the bases of the bullets, I would risk using the cases.
However be aware, those rounds are on the market because Korean Ammunition specialists decided the stuff was either unsafe to store, or unsafe for their troops to use, or both. There is risk with old surplus ammunition.
These are from old, 1969 and 1970 safety reports. You can see that forty years ago the US military was demilling thousands of old WW2 ammunition.
