Due to an oversight, the Iron Bomber's projectiles use the explosion sound effects of the Air Strike rather than the custom ones made for the weapon by Valve.

On line 19099 of items_game.txt, the game calls for the "Weapon_Airstrike.Explosion" effect to be used rather than the expected "Weapon_TackyGrendadier.Explode" (sic).

Replacing this causes the projectile explosion effects to work as intended.