Long Steel Barrel
His iron counterpart is made on the same way, but with, obviously, Iron. The barrel former can be the quality one or the stone one
Short Iron Barrel
As is name suggests, is made of Iron. 2 ingots actually (With Steel you get a Short Steel Barrel), and a Barrel Former. The barrel former can be a single use only or a quality one
Barrel Former (Single Use)
Crafting of a (single use but) useful tool. Edit: 1.1 for the 1.15.2 version lasts 3 times before breaking. Edit 2: 1.2 for 1.15.2 version just require cobblestone instead of Quartz. Edit 3: Newer versions requires an iron ingot in the center.
Example of a gun craft
The most basic weapon of all the mod: The Tanzutsu
Caplock Cap Cone
The weird thing on the Caplock Mechanism. And yes, that's an End Rod. It was designed to be an end-tier item.
Now, the bullet.
You can use either paper...
Basic Bullet
The Crafting Table Recipe yields 4 Basic Bullets
Flintlock Mechanism
For the Flintlock Guns. Not only they deal more damage, but they doesn't get wet under the rain so easily.
Quality Barrel Former
This one last forever!
Steel Nugget
Made from heating up Steel Slag. (Should) Only work in Blast Furnaces on 1.14.4 and up.
Matchlock Mechanism
For crafting the Tanzutsu and the Arquebus
Steel Ingot
Yes, is the normal recipe.
Or Wool!
This recipe and the with-paper one are the same in all the guns, but...
Flintlock Musket (Legacy)
A large weapon. More range, damage, and cost. Most rifles are made this way, but its barrel changes. Matchlock and Flintlock muskets are made with iron barrels and their respective mechanisms. The Caplock Rifle is the only one that needs the Steel Barrel.
Small Handle
The most simple and basic recipe of all the mod.
Caplock Mechanism
The most advanced of them all! (But with the most simple and powerful weapons to program!)
For reloading...
You must use this in order to charge your weapons with gunpowder and bullets. Is called a "Ramrod" (Legacy). Now, the Ramrod has been changed of texture and recipe, requiring leather instead of wool, and removing the need for iron nuggets
Wooden Stock
More expensive, for more firepower!
Reloading:
First of all: Put the Gunpowder in the gun with a Ramrod.
Steel Slag
A basic resource for more powerful weapons. (Legacy) Edit: Now, it is done with 3 Fire Charges, 5 iron nuggies and 1 coal/charcoal.
Bigger gun = Bigger consumption
The Musket, Rifle and the Arquebus uses 2 gunpowder. The Flintlock Pepperbox stills use 1, so don't worry. PD: The Ramrod last forever! (Legacy). In 1.14.4+ and up, the Ramrod should have durability