"Lots of external factors effect pressure/temp during ignition of a powder charge. The most important factor being barrel steel temperature. Compare the ignition cycle of the same rifle at two extrem temperatures. If a rifle is minus 100 degrees Celcius when it is fired, the barrel will suck many calories from the chemical reaction of the propellant, muzzle velocity will be reduced because heat was robbed from the reaction and lowered chamber pressure.
Compared to the same rifle fired at 200 degrees celcius. The barrel steel is three hundred degrees warmer, and while it is still much cooler than flame temperature of the powder charge, it will absorb much less heat from the reaction than the colder barrèl. Possibly allowing temperature and pressure to elevate far enough to become dangerous."
i'm neither physicist, ballistician nor engineer but, in your example of a barrel at -100 degrees or 200 degrees if the cartridge is room temperature when placed in the chamber and fired is there adequate time for barrel temperature to have a profound effect on gas pressure or volume ?
thanx
