Self-ignition catapult bolts?

[M. Demetrius]

I have made fire by friction with a "fire-bow" and board, but it's a) not at all like you see in the movies, and b) not as easy as it sounds. You really don't make fire, though, just a glowing ember that can be blown against tinder to make a fire.

Without chemicals to help with the combustion, I agree with those who have said they doubt it could be done just by air friction, of the 1/100 of a second the bolt is in contact with the ballista as it moves off the launcher.