Well I don't have the PhD in physics that you apparently do, so was simply passing along a caution I have seen printed in pretty much every reloading guide I have ever read.
Neither do I. But I do have common sense, a commodity in low supply on the internet. A weak sheet metal ammo can will burst well below detonation pressure, which it would need to be considered a bomb.
My point is; it would shield the contents from the high heat necessary to ignite the contents. In a total burn down of a house, nothing is going to prevent powder from burning. But enclosed in an ammo can, it would be nearly impossible to ignite the powder inside.
I checked 3 sources of reloading books/manuals. Hodgdon, Hornady and the lyman 48th. Hodgdon says;
°"
Storage cabinets should be constructed of insulating materials and with a weak wall, seams, or joints to provide an easy means of self venting."
°
Obey all regulations regarding quantity and methods of storing. Do not store all powders in one place. If you can, maintain separate locations. Many small containers are safer than one large container.
Nothing was said about ammo cans.
Lyman says it about as close to telling us not to store powder in a strong container.
Caution: "In case of unintended ignition it is imperative that the storage container have one or more weak walls that will open out at very low pressure to vent gases before they can cause damage. Using a strong enclosure may cause a burst of considerable force causing property damage or personal injury."
Hornady has one paragraph about powder, no precautions about storage. Just a brief description about the properties of smokeless powder, followed by a burn rate chart.
You are right in that powder stored in an ammo can would burst at a higher pressure than if the bottle/keg were NOT in any container. But it wouldn't be a bomb.
I'm not about to try it to see what happens. I much prefer to be on the outside looking into a jail!