Surely Hollywood does not lie?

[Q.E.D]

And why does every handgun in the movies sound like a cannon?

But I can see a tracer bullet causing an explosion. Magnesium burns very hot.

[Rick]

*Originally posted by Q.E.D. *
**Th ignition temperature of liquid gasoline is about 600 degrees F, while the temperture at the tip of a lit cigarette is about 300 degrees F. So, no, a lit cigarette can’t ignite liquid gasoline like it does in the movies.

Regular lead bullets won’t spark, but steel jacketed ones might, and could potentially ignite a pool of gasoline. But it isn’t very likely. **

Whoa! back the truck up there Q.E.D.
Where did you get those numbers?
According to the MSDS for Chevron Supreme The flashpoint of this gas is -49F and its autoignition point is 536F.

According to this site flash point is defined as

Flash point is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid. The lower the flash point, the easier it is to ignite the material…A closely related and less common term is fire point, the temperature at which the flame becomes self-sustained so as to continue burning the liquid (at the flash point, the flame does not need to be sustained). The fire point is usually a few degrees above the flash point.

and autoignition is defined as

The autoignition temperature of a substance is the temperature at or above which a material will spontaneously ignite (catch fire) without an external spark or flame.

so it is pretty clear that a 300 degree cig could ignite gas.
So why doesn’t it?
Gasoline will only burn when its vapor is in a narrow range of air fuel ratios. A bucket of gas in the open will be too lean to ignite. A gas tank will be too rich to ignite. But if the mixture gets just right, a spark will set it off.
One more misconception that I want to clear up. Luquid gasoline will not burn. Only the vapor.

[Q.E.D]

I used a pyrometer to measure the temp of a cigarette (couldn’t find a cite online), and got the ingition temp of gasoline from here.

Natural gas has a high ignition temperature, about 1,200 degrees Fahrenheit, compared with about 600 degrees Fahrenheit for gasoline.

[Q.E.D]

Also, flash point is not the same as ignition temperature. From your cite:

“Flash point” means the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid…

From this site:

Flammable (explosive) range of flammable liquids is the percentage range of liquid vapor in air, by volume, within which ignition can occur. Gasoline, for example, has an explosive range between 1.4% and 7.6%. This indicates that any concentration of gasoline vapor in air between these percentage limits will ignite at any temperature above -45F (flash point) when an ignition source provides a contact temperature in the range of 500 to 800 F (ignition temperature, depending on type of gasoline)

[MonkeyMensch]

*Originally posted by Hermann Cheruscan *
**… Even super hot tracer rounds. **

I got to disagree with this one. P-51’s regularly recorded strafing supply trains with unspent aerial dogfight ammunition in WWII and the results were, wel let’s say unequivocal.

But as the previous posts have hinted at, I bet they wish they had pure tracer loads at that point.

[hammerbach]

I’ve fired tracers that ignited small grass fires - I can’t imagine that they wouldn’t ignite gasoline.

[hammerbach]

Oh, and welcome to SDMB, Pasty2003.

[Rick]

Q.E.D. no offence, but I will take Chevron USA as a better source of information about gasoline than a site pimping the advantages of Natural gas as a fuel. Now since Chrevron says in their MSDS that gasoline will autoignite at 536 F that would seem to blow, er burn, your 600 F sites out of the water.

[Q.E.D]

You’re neglecting the second cite, Rick. I’d think Ohio State University would be a pretty reliable source of information, and they give a range of 500 to 800 degrees F, which is dependent upon the type of gasoline. Nevertheless, the lower limit of 500 degrees is still less than the temperature of a lit cigarette, which was my original point. I stand on my assertion.

[Ethilrist]

Yes, it does, and don’t call me Shirley.

[sub]I cannot believe that nobody’s posted that yet…[/sub]