I have been a proponent of using old powder for my entire life. If properly stored powder will last indefinately and especially in the new style plastic containers that will never rust out.
I went to my local club meeting and a friend gave me an unopened can of IMR4895 made in 1980 and stored indoors for the whole time.
I just finished loading my can of 4895 from 1978 and it was fine, however when I opened the can he gave me it looked and smelled odd.
First; there was fine rust dust in the powder, and obviously the can had started to rust on the interior. This showed up as billowing red dust when I poured some out.
Second; the powder did not have the standard blue black graphite look to it. It was slightly yellowish in color. Especially obvious when compared to the good stuff.
Third; It didn't pass the smell test. It had a distinctive "sweet" smell to it.
It is now fertilizing my wifes roses.
This is the first time in my 40 years of reloading that I have ran into bad powder.
I'm just glad I had read enough in books and magazines, to know how to recognize it when I saw it.
Randy