Is powder temperature sensitivity over blown?

[lazyengineer]

I'm unsure if a temp insensitive powder will have better ignition/combustion at low temperatures? If you switched 748 for another powder with the same "weak" primer, did it run fine in the cold? If so what powder did you switch to?
Actual experience is invaluable, my thanks to all who share.

It's a good question, but probably not. The little research I've seen on primers varies from "very little" to "practically none". But I wouldn't call that definitive. Essentially though, those statements do make some sense. The energy content of a primer is released all at once in an explosion. Which has so many KCal of energy release upon the instant chemical conversion of the reactants. That propagation happens all at once, or at least, at a rate that is faster than the shock-wave, which is an explosion. Cold or hot, about as much energy is coming out of that primer regardless - minus the sensible heat effects of the cooler T, which is fairly neglible.

Gunpowder is much more complex, and is a slower reaction. While it too contains a certain amount of KCal's, and upon full reaction, will essentially also release all of it regardless, is true. But Gunpowder is a complex reaction propagation, where the conditions affect the propagation, and the propagation affects the conditions, which can affect the final energy release and extent of powder consumption. Where the reactants are combusting at a rate slower than the pressure wave propagation. The initiation of the reaction requires enough heat from the primer to start the reaction of the gunpowder, and enough of the gunpowder to generate enough heat, to self-sustain propagation. Which is why ball powders are more difficult in cold weather, because a stick-powder has an edge to be immersed in the primer flame, light, and propagate. Spherical powders are smooth and don't have corners to be bathed in flame. So they are harder to start. In addition, a gun powder reaction rate and energy release is dependent on how hot its neighboring molecules were and are firing it up, and how cold it is, and it's other neighboring molecules are, soaking up the heat. Colder powder can have a slower absorption, or straight up insufficient absorption, of the primer heat, and a slower propagation of burn rate while heat is being sucked up warming up the molecules more first, to finally exceed the activation energy to react and light. A slower reaction means less powder was fully consumed in that initial critical first 1-2" of bullet travel, where everything is immersed in the maximum temperature and pressure plasma. Once the bullet gets past this point, the reaction rate is quenched by the bullet travelling down-bore releasing the plasma pressure (and temperature). You can still get some burn, but very little compared to peak Temperature and Pressure rates in those first couple of inches. (Hence, fast powders with fast burn rates for large ratio of bullet diameter to reaction chamber (i.e. pistols and shotguns), vs small diameter ratio to reaction chamber (rifles). If the powder starts cold, and is a composition where it's difficult to light due to heat-transfer properties (i.e. a sphere vs being a stick with sharp edges), and is a composition that has a higher activation and/or heat capacity; cold weather and cold components work against you.

one interesting part of all this is that cold barrels, are actually quite important as well; even if the ammo is loaded warm and quickly fired. Because that can be a heat-sink for one thing, I suppose; but that's what I read.

Or at least, that's how I look at it - not my area of research and expertise, but that's my best explanation on why cold is more important in regards to the gunpowder, than the primer.