Jim,
Yeah, blending was my only term, originally. I got milling from someone who is in the trade and says milling is frequently used here. I don't know why. He says folks would be astonished by some of the horse-trading and sourcing practices in the powder business. He says he's had Hodgdon folks bidding against him for the same surplus lots of powder. Where they end up, I don't know, but Hodgdon claims they don't supply manufacturers other than some very small specialty places. The bottom line is that it is difficult to know what age your powder really is, and you don’t normally have a storage condition chain of custody or history that comes with it. I think these factors explain a good number of the recall notices that have occurred in the past.
In addition to the total recall of all
IMR 4007 SSC lots, there have been past lots of 4350 and N140 recalled for premature deterioration in the past. There are also less specific recalls for other powders like Accurate 2520 and Ramshot Hunter that simply warn that high pressures can occur. More premature breakdown? Wrong packaging? Bad "blending" or "milling?" here is another unfortunate situation in which pressure can be increased because the stabilizer has been consumed, and the deterrents have then been attacked faster than the powder mass, leaving you with what amounts to a reduced charge, but a reduced charge of much faster-burning powder that can raise peak pressure appreciably, while actually lowering velocity due to the loss in total gas volume.
The Happy kaboomer,
No. Smokeless powder will not last forever, even in good storage conditions. This is why the military puts time limits on stockpile storage. When smokeless powder is manufactured, it has a stabilizer chemical included in the mix. Usually, it is the antioxidant diphenylamine, though others have been used. Nitrocellulose and, in double-base powders, nitroglycerin, regularly experience the spontaneous breakdown of individual molecules on a random basis. It is the result of how heat energy distributes at the molecular level, occasionally making a momentary high temperature occur in an individual molecule that breaks it down. When that happens, nitric acid radicals (what makes the acrid smell and sometimes red vapor and red dust in a powder that has gone bad) are released. Allowed to run loose, the acid attacks other molecules, and this is what initiates the snowballing breakdown effect. The role of the stabilizer is to capture and neutralize acid radicals before enough of them accumulate to cause that problem. However, over time this constant low-level neutralizing of acids from spontaneous molecule breakdown uses up the stabilizer. Once it is gone, there is no longer a brake on powder deterioration.
While it's not often that powders go south, it just isn't never. As I mentioned earlier, I've had it happen twice. It is a good general practice whenever you open a container to waft the air from the top toward your nose for a quick sniff to check for the scent of nitric acid. The odds are you will only smell ether or other solvent odors, and those are normal. But nitric acid, while it doesn't smell exactly like vinegar, is closer to that than the solvents are. I think you'll know it when you encounter it.
