I picked up some new, but old stock 7mm Remington Mag brass. Headstamp is winchester Super X if i recall correctly. There is some black spots on the brass, some looks like stains and cant be felt, some can be felt by running my fingernail over them.

Some of the worst spots are inside the cases that i can see by looking inside with a flashlight.

Is this some type of corrosion?

Safe to use or should i scrap it?

Clean it, then shoot it!

Just rub the spots with some fine emory cloth before tumbling.