I have some older German surplus ammo that is a little tarnished but not corroded. Can I freshen it up with a bit of Flitz?

I've used very fine steel wool (00 or 000) to clean up tarnished ammo before. Just wipe it clean with a clean dry rag after

If it's DAG or MEN... Read THIS first:

http://m14forum.com/ammunition/108956-pictures-corrosion-inside-men94-cases.html

I pulled all mine down for components.  It's OK to use the powder, just shoot it up instead of storing it.

Also, my guess is that Flitz is bad news... probably has ammonia in it which weakens the brass.

Flitz is great- put the ammo in a vibratory tumbler with clean media, squirt some flitz in, tumble for a couple hours.  Flitz also makes a special version just for cleaning brass.

It has been proven repeatedly that tumbling loaded ammo does not break down powder.

I am currently cleaning up some 223 ammo that sat in mags for 15 years in the garage and the brass on some is ugly.  Some fingerprints also etched in the brass from loading.  Works great for cleaning the ammo up.  Have used this method on lots of ammo over the years.  Wipe off the cleaned ammo with old rags or towel, and wear gloves to keep from putting oily fingerprints on it.

Now I wear gloves when loading mags for long term storage, put in cans with desicant, and don't have the corrosion problems.  I have cleaned up some ugly ammo over the years, I dont want my rifle's chamber having to deal with gungy ammo if I can prevent it.

If after cleaning you can see that the corrosion was more than surface layer, you can pull it down for reloading the bullets.  I would not recommend shooting ammo with questionable brass like the DAG or MEN in the upper linked post.

In that case, I'm going to buying some Flitz.  It works damn well, if I remember correctly.

I tried the Flitz on a few 7.62x51 rounds and it cleaned them up very well. Out of 500 rounds, I only have one that has what appears to be a crack in it. I ditched it just in case. The rest look great.

Same here with a bucket of Port that has the nasty green stuff on it... steel wool, flitz, shop towel... and all cleaned up well. Shot well too...