Briman think about your logic. "Cool air" or ambient temperature is cool too stationary objects. BUT too an object moving 3K fps that same air creates friction and that friction heats up that object. A centerfire rifle bullet moves fast enough to create this friction. As does airplanes like the SR-71 Blackbird and the fastest jet fighters of today. The SR-71flew at altitudes as high as 100K ft (at which the airtemps would be in the 50-100 below0 range)yet the skin had to be made of titainium and othertrick alloysto withstand the friction and heat as it moved through even the extremely thin air at such altitude. (Sidenote, that aircrafts skin became so hot during flight that it would "recure/retreat" itself, the useful life of that skin was thought to be nearly forever!)

The space shuttle (and any other spacecraft) returning through the earths atmosphere is another example of this "air resistanc/friction induced heating". The space shuttleusually orbited the earth at 17K too 20K mph. Yet because once it was out of the earths atmosphere there was no air in space to offer that resistance. Yet we all know as evidanced by the Columbia disaster, that once the space craft encounters atmosphereat about 500Kft (which is simply extremely thin layers of air) great amounts of heat were encountered until the space craft slowed too a speed (below about 1500 mph) at which the air resistance (friction) would no longer build heat.

I can see where a pistol bullet would NOT cause ignition of something like a can of gas or a tank of propane. But try that same "experiment" with something like a .270 or a 7mag and see what happens. Most handgun bullets are traveling about 1/2 too 1/3 the velocity of modern centerfire calibers. A similar "effect" can be noticed while shooting a gallon jug of water with a 9mm and then trying the same thing with a 30/06. The end result is MUCH different!

Like I always say... SPEED RULES!!!
RA