I once heard on GunTalk's podcast that burning powder (in this case Accurate #9) burns like paper. I'd like to correct that. It burns like a flame thrower! I almost set myself on fire. Be careful with your powder and how you store it.
It appears that about 10% of the powder in these cases went bad. I just emailed Western Powder and sent them photos to get their take on it. The powder was new when the original 1lb container was opened and the loaded rounds have only been on the shelf for a year. I'll let you know what they say.
I sent an email to Western Powder yesterday, and I've been going back and forth with the ballistician throughout the day today. He said that he's never seen anything like this in 40 years, and that modern powders have a shelf life of 30+ years. The only thing he can figure is that it's a chemical reaction with the primers. He also asked me if I cleaned the cases with anything that could have left a contaminant. I checked this bog and it records that I haven't since 3/09, which was 9 months prior to the time when these cartridges were loaded. The primers seem to be the best answer, but I'm going to see if I have any other rounds loaded in 12/09 and if so, I'll pull the bullets and get back to you. I should get a pipe and Holmes hat, but there's no smoking allowed around gunpowder.
Pulled 150 more and this time only 3 were bad. I was thinking that these were loaded prior to having a tumbler. Could a dirty case have contaminated the powder?
Johan at Western Powder responded: "As I suspected it appears that some primers are decomposing." Now the question is "Why?"
"Bob, The worst will be that these primers will not deliver enough or any energy at all. This may result in “misfire” or “hang-fire” or “squib” load which may also result in a stuck bullet in the bore. Although not dangerous by itself, if not noticed in time a 2nd bullet can be jammed behind a stuck bullet. It’s also quite a struggle to remove a stuck bullet (or more) from the bore without damaging the barrel and should only be done by a competent gunsmith. Regards,
Johan Loubser, Ballistician, Ramshot.Accurate.Powders"