Use the following items at the Forge to upgrade the corresponding weapon.

Item	How to unlock
Something Burnt	Galleon Mortar.
Something Coarse	Scrap Musket.
Something Fancy	Army Carbine.
Something Foul	Fire Bellows.
Something Greasy	Dueling Pistols.
Something Heavy	Cael Hammer.
Something Nasty	Fang Repeater.
Something Pointy	Brusher's Pike.
Something Sharp	War Machete.
Something Stringy	Breaker's Bow.
Something Wrong	Calamity Cannon.