I apologize, I just found some info in my old 3.0 DMG on dynamite.
Dynamite - 3d6 blast damage, 5ft radius, fire damage, dc 20, 1/2 damage. increment of 10ft, weight 1lb.
Not sure what happens if you were to strap that to an arrow though. I'd imagine the chance to hit would drop. -5? -10? Not sure.