That's interesting. Lead doesn't glow even when it's molten.We did a night shoot at a Boy Scout camp with .22's once and I remember seeing the bullets glowing red as they made their way down the range.
Must be the copper jacket. So, why are bullets never glowing in other photos?
I'll add the fact that the bullet has been hammered by the explosion, and followed by fire for a period of time. The air in the chamber has been rapidly compressed with the detonation so it too is superheated.Don't ignore the friction between the barrel and bullet -- I suspect that might be the biggest heat source.
He said that if the bullet is not resting in an area that it can do future damage they generally leave it in there for 2 reasons. First, bullets get so hot that they are always steril when they go in and even if they pass through something that is not steril they are hot enough after they stop to completely cauderize the flesh surrounding the bullet wound.