Quote Originally Posted by dclare4
I experimented with this some time ago but I fear my experiments were for naught (though I was probably doing SOMETHING wrong somewhere) but apparently one can't let non-fire weapons shoot 'fiery' projectiles - the fire arrows themselves are options for bowmen only - which is really rotten as the 'fire weapons' are the closest thing to simulating the effect of early musketry. If you're going to experiment best of luck and do tell us if it's possible.

Cheers,
Lord Clare/Harlechman
In fact, you can make flamming missile different from arrows.
It is an old question reported long time ago:
https://forums.totalwar.org/vb/showthread.php?t=43671
As you can see, we are using flamming javelins (falaricas) in Iberia Total War from the very beginning of this mod.

I didn't explore the modification of the visual effects (smoke, particles, etc), but I imagine that it would be possible too, at least from what is said in this tutorial:
https://forums.totalwar.org/vb/showthread.php?t=55912

I didn't test with slingers, but I suppose that it would be also possible to make a fiery_bullet projectile, as a first step to fire weapons.

Cheers.