The whys and wherefores of nitrocellulose (or Cellulose Nitrate) stability is a very involved topic. This is an interesting document, of which I have only copied a few paragraphs. Cellulose nitrate stability is a real concern with museums. You can read about the fears of old film stock autocombusting, and more interesting, the forgotten history of nitrocellulose film stock autocombusting and burning down movie theaters, with of course, loss of life. Those forms of cellulose nitrate are less highly nitrated than gunpowder, but they still will catch fire.
The Use of Cellulose Nitrate in Art Conservation
Dr. Charles Selwitz Getty Museum
https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/nitrate.pdf
Cellulose nitrate is the polynitrate ester of the natural polysaccharide, cellulose, and for a polymer averaging 2.3 nitrate groups per glucose unit has the structure shown in Figure 1. The molecular weight for most commercial products ranges between 20,000 and 250,000. This semisynthetic polymer was first produced more than 150 years ago and is the most important and only commercially available inorganic ester of cellulose. Due to its unique physical properties and low cost it has been an important factor in many advances in the industrial arts and sciences over the years. Cellulose nitrate was initially used in the manufacture of military explosives where it came to be known as "gun cotton," the first major development in explosives since the introduction of black powder. When it was discovered that cellulose nitrate could be stabilized with camphor (in the ratio of 4:1), the resultant product, celluloid, inaugurated the advent of engineering plastics
In the years following World War I, cellulose nitrate lacquers and coatings were developed. While these have since been superseded by better materials, the largest industrial use today of cellulose nitrate (now also referred to as nitrocellulose) continues to be in its capacity as a lacquer, although substantial quantities are still used in explosives and propellants, printing inks, and plastics. Currently, the total commercial production of cellulose nitrate in the United States approaches 100 million pounds a year
in terms of stability, however, cellulose nitrate is a very suspect material. It does not have the resistance to degradation possessed by most other polymers used in conservation. Only when stability is defined as "the maintenance of solubility and reversibility" can cellulose nitrate, which degrades, but generally does not crosslink, be said to have stability
Chapter 3 Causes of Instability
Most of the literature on cellulose nitrate instability describes three primary modes of decomposition: hydrolytic, thermal, and photochemical. These modes are examined in this paper with concern for rates and mechanisms most likely to prevail under ambient conditions. Recent research can be interpreted to show that these three modes can be redefined into more fundamental mechanisms for primary decomposition, a finding that may provide additional insight into the properties of the polymer as well as the optimum conditions for its use. Primary decomposition processes slowly lead to breakdown products. If these are not swept away they can lead, catalytically, to a faster and more extensive degradation than that caused by the primary processes that engender them. Conclusions on the chemistry of decomposition caused by these breakdown products, i.e., secondary processes, are integrated with our analyses of the primary modes in the next section-a discussion on the overall stability of cellulose nitrate at ambient conditions.
Hydrolytic Decomposition via Acid Catalyzed Ester Cleavage
The earliest manufacturing processes of cellulose nitrate in the 19th century were concerned almost totally with the production of explosives. After a number of disastrous detonations took place, the search for their causes revealed in 1865 that the retention of small amounts of sulfuric acid from the nitrating mixture was responsible for the instability (Worden 1921:1604 et seq.), and, further, that this instability was roughly proportional to the amount of sulfuric acid left in the polymer (Wiggam 1931:536). It was also recognized that sulfate esters of partially nitrated cellulose were also formed (Hake 1909:457). In no case did the nitration of cellulose with mixed acid ever proceed to a completely nitrated product, i.e., to a D.S. of 3.0 and nitrogen content of 14.1%. The best that could be achieved was a product with 13.8% nitrogen in which only 29 out of 30 hydroxyl groups bore nitrate functionality because the 30th was converted to a sulfate ester. In cases where exhaustive nitration was done without using sulfuric acid, e.g., with nitrogen oxides (Bouchonnet et al. 1938:308) or with nitric acid and phosphorus pentoxide (Lenz et al. 1931:4) or acetic anhydride, a completely nitrated product 15 Instability with 14.1% nitrogen was obtained. These products were invariably of better stability than high nitrate product made with mixed acid (Barsha 1954:724-30).
The lifetime of your cartridges is not just a simple of where you store your ammunition, but storage is very important, particularly temperature. This is from a Nato specification, I removed the number due to the number of conspiracists who discounted the information because they believe Nato is out to create a one World Government.
Gunpowder deteriorates exponentially with temperature.
I found this chart from a 1970 Symposium, it more or less shows what the Army was doing in terms of stockpile reliability testing
The thing is, the lifetime of gunpowder is an unknown, and it has to be determined by testing.
For those who have WW2 era 4831, well I have some. And I have some cartridges loaded by the man who gave me a can of the stuff. The ex Gun Club President sold me a 300 Win Mag and tossed in ammunition he had loaded with WW2 surplus 4831. I cannot say it was IMR 4831 as it could have been made in a military Arsenal. Pres says the stuff was so cheap one of the guys on the buy was using it as to light the charcoal for his barbeque!
Anyway, I started going through the ammunition and became very concerned about the boxes loaded with “H4831” or simply “4831”. I verified with Pres that was his notation for the WW2 era 4831.
The powder does not look gummy or dusty. Is it safe?
When Pres gave me the can (2013ish) I took it out and tested it with new IMR4831 in a 270 Win rifle. I did not notice any anomalies. It burnt faster than the new stuff, but, this is not blended IMR 4831. The stuff we get is blended to an average pressure curve. The military has its own pressure gauges and chronographs, so they test lots and determine how much to put in the case.
So again, is it safe? Heck if I know, what I do know is it is showing signs of deterioration. I sure as heck discarded the corroded 300 Win Mag cases, and the old powder. The thing is, for me, there are a number of known unknowns I have about old powder. I don’t know how to tell if the burn rate is unstable before shooting it. I did have sticky extraction with “funny” retorts with military pull down IMR 4895. That powder looked good and did not smell. It also cracked the case necks of 700 LC308 brass. I considered those signs as a portent of evil things ahead, so I stopped shooting the stuff. I also don’t know the level of deterioration it takes for smokeless propellant to detonate.
Old gunpowder does not burn predictably as the shape and chemistry of the grain has changed. It may not blow up your firearm each and every time, but there are plenty of blow up reports with old factory ammunition. Notice in all the powder recalls in magazines, a warning not to load ammunition with the deteriorated gunpowder. A huge concern with the Insensitive Munitions community is keeping deflagrating propellants from transitioning to detonating propellants!
https://en.wikipedia.org/wiki/Deflagration_to_detonation_transition Energetic propellants should not be considered 100% predictable, nor something under your control. * Everything I have read indicates the Insensitive Munitions community would like a solid and definitive theory of burning, but they don't have one. They have empirical models, and there are limits to their knowledge, such as the exact conditions that it takes deteriorated powders to develop burn rate instability and detonate.
This writer had 1960’s 22 lr blow up his pistol.
Why Did My Gun Blow Up? https://www.activeresponsetraining.net/why-did-my-gun-blow-up
Some people want absolute certainty before they will commit to a path to action. Life is seldom that certain. Anyone remember the Surfside Florida Condo collapse?
https://en.wikipedia.org/wiki/Surfside_condominium_collapse The condo owners totally ignored and disregarded the severity of the structural issues of their building. The geezer condo owners preferred to kick the maintenance can down the road. For the old folks this was an economically rational decision. Why spend money now, when their life expectancy is less than the building? So, they took the risk of having the building fall on them while they were still up right. Ninety eight of the condo owners did lose that bet when they were crushed in the collapse, and the living all lost their condo’s. But the Gods do laugh, except for those who lost their lives, the survivors came out winners as they sued enough entities to get an award of $1.0 billion dollars!
If you can sue someone when the roof falls on top of you, maybe the termites eating the structure of your house are actually doing you a favor. Or your grandkids a favor, assuming you get flattened. Seems our society is based on the concept we are all victims of somebody. Maybe someone knows the odds of winning a case against an ammunition company when something goes bad with your old ammunition. It used to be ammunition companies warranted their ammunition for ten years. Now it looks like, one year.
https://www.cci-ammunition.com/warranty.html
Warranty FEDERAL PREMIUM – CCI – SPEER – BLAZER – AMERICAN EAGLE LIMITED WARRANTY
CCI/Blazer warrants its ammunition and primers to be free from defects in workmanship and materials for a period of one (1) year from the date of purchase. This warranty is extended only to the original consumer purchaser. 
