When powder goes bad, it is amazing how quickly it happens. Usually there will also be some expansion of the container. Some powder actually clumps and has sweat which becomes oily. Others turn "rusty" when they deteriorate and the smell is immediately noticeable as soon as the can is opened. Don't go sticking your nose into the can and take in a whiff, those fumes are toxic. I have had powders go bad even though I stored them properly. Three different types. Two were extruded and one was ball. The first time it happened was with Nobel #44 a surplus powder that was very close to being IMR3031. I had it in seven pound cardboard containers as well as one pound cans. This stuff was cheap even back over 35 years ago. The first lot was purchased in 1970 from Tom Higginson. I liked it a lot and at that time I was shooting a lot of 303 Brit, 7,62x51, 30-06 and 7x57 along with 6.5x55. This powder gave acceptable results in all of these cartridges and I shot a lot back then.
The next powder to go was also from Higginsons and went by 4350OEM. It was also an extruded powder but slower than the #44.
Both of these powders deteriorated in exactly the same manner. The containers were slightly expanded and all the metal interior surfaces were rusty. I noticed the rust from the ends of the cans which were metal on the powder below so I cut open the paper side wall and took out a sample. There was no color change. The powder looked normal on both types other than some clumping an unusual amount of dust. The smell that came out of the cans was acidic. IMHO the rust is coming from metal and is a darn good indication not all is well. The dust on the other hand is a definite indicator that all is not well as is the clumping. I am not talking about a coarse type of dust from broken or damaged kernels. The dust I am indicating is as fine as talcum powder and is caused by the coating on the kernels breaking down.
The third powder that went bad also came from Higginson and was a ball powder called N160 which was a ball powder with IMR4350 qualities bit slightly slower and oh so consistent in performance with heavy bullets in the 338-06. This stuff clumped, sweated and gave off gasses that caused the cardboard container to crumble in one case and also caused the metal shelves to rust. The whole room smelled like acid fumes. I really miss that powder.
Old Tom Higginson was a friend of mine and he was as close to being an expert on powder as you can get. About the only person that I know that might be more knowledgeable is Ganderite. No offense Bruce or Eagle Eye but we are limited to the powders we can use or purchase then apply to our needs. I used to get test batches of powder from Tom so that I could experiment with them and give him the results such as velocities from a Chrony or drop rates at specific ranges which were far better indicators of velocity than the Chrony ever was. He always supplied me with a number, manufacturer's product sheet with appx speeds of the powder as well as a faster and slower equivalent that could be found in the several reloading manuals I had on hand. As often as not these were not just surplus commercial powders but powder that came from pulled military cartridges. Often there was a lot of fmj bullets available for testing as well.
Tom was always above board with his offerings. If the powder was old surplus war stock he made sure his customers knew and the powders were extremely cheap.
Now, one thing that I must make a statement on. NOT ALL POWDERS ARE THE SAME COLOR. Most are a dark gray because of the graphite used to coat the kernels and therefore control the burn rate. I have flake powders on hand that are yellow and perfectly fine. I also have RED (rust colored) powder which is just fine as well. The brighter colored powders came from cases that were loaded with wooden projectiles and are both over 60 years old and are in line with Unique. I also have an extruded powder that is older and is very consistent but produces low velocities and is an opaque green in color. I don't have a lot left and like to use it in cases like the 8mm Kropatschek. I have no idea what it was first used for or intended for. Tom sent it to me and told me he only had about ten pounds of it an if I didn't want to try it for something to spread it in the garden. I took a chance with it in a rusty model 99 Arisaka and found I couldn't put enough powder in the case to create more than about 35,000psi from what I can deduce from other loads from Lyman equivalent velocities.
To make this diatribe short, smell and fine dust are far more indicative than color. But if I come across rust particles in any lot of powder I would be very careful and set it aside or if it is just one pound, throw it in the garden.
