I recently came into possession of old military issued ball ammo with some corrosion issues also. Considering the amount I received I thought it would be worthwhile to see if they where still good to go. First step was research, I found this great post on .303 ammo, it might be posted already somewhere here but here is the link http://carteach0.########.ca/2008/11/corroded-ammunition-thoughts-and-images.html From there I looked over each of the rounds and separated the ones I thought where suspect. I then hand cleaned each round with brasso using my fingers to rub the brass. This gave me an idea of which cases maybe pitted with corrosion, I was also looking for any primers that maybe bulging. Every one of them was smooth, stained with discolouration but nothing that really made me worried. I then took some of the suspect ones apart to see how the powder was and even on the most corroded one the powder was good and dry and lite up easily.
Disassembled round
Nice dry powder
Here is a few photos of the worst primers
And here is the worst case
Yesterday I went to the range with the express purpose of shooting some of this older ammo. I brought out the worst of the batch and fired 15 rounds. Still have another 130+ rounds dating back to the 40's
So armed with my 4 mk1 British Lee Enfield, a bunch of old and new Remington rounds and a bottle of Windex I hit the range.
Out of the 15 rounds I had:
2 round that had a small delay, enough to hear the click, hear a fizz and feel a bang. Rather than everything happening at the same time
2 rounds that where complete duds, good primer hit but nothing.
All other round fired fine
I did have 1 split case
And that one came from my oldest round in the batch
They seemed to kick a little more than the normal Remington that I used afterwards but overall I felt safe firing older ammo.
That being said I would go with some of the other comments, if YOU feel it's not safe, then do not fire them.
If you only have a few rounds then dispose of them, why risk it
And yes I highly suggest to bring a bottle of Windex if you are to shoot these older rounds. After firing soak everything and then clean like there is no tomorrow