Just got a few boxes of OLD Speer and Hornady bullets for the 35 Whelen. Some of the jackets are partially or completely tarnished -- they look like an old penny. Is it OK to shoot these, without worry about damaging the bore? I don't know if copper oxide (or whatever it is) is harder than pure copper.

Just throw them in your case tumbler with fresh medium....

Ric is right, I polished some old 30-30 160gr. RN last nite then loaded them look like new. and have shot polished bullets before they work fine.luck hotdog

I would just load them and shoot them As long as they are no growning green stuff.

I am with P Dog, load them and shoot them.
Unless something is growing on them.
Good luck and good shooting.

No wrong answers here, so far. On exposed lead spitzers, tumbling can "round" the nose a bit, but this is usually negligible. I agree that if they are not green, they'll shoot fine. Tumbled, you can hardly tell them from new.