Feat: Custom Feat "Instant" is taken for this.

"Javelin Throw" or "Heroic Throw" will now allow you to deal ranged damage to an enemy if you have a spear in your hand. You will throw your weapon, forcing it to be dropped back into your inventory, and the target will take 1d8 + 2*Str Modifier Damage. You cannot use this feat with anything that isn't a trident or full spear.

DC Cost: 2

Below is DM info
File name: ft_javthrow
Subtype: 2
Type: 1 = instant.