THE CONCEPT
The idea to add muskets to the world of Skyrim seems logical. It has been 400 years since the Oblivion Crisis, and it seems illogical that the technology of Tamriel has in fact regressed rather than evolved. How can the Imperial Legion wear Roman style leather armor, when they wore full plate in Oblivion?? Illogical?

I REFUSE TO ACCEPT THIS NONSENSE!
Guns, including cannons, are mentioned in the Elder Scrolls lore, including Redguard exploding black powder, cannons mentioned in a Daggerfall joke book, fireworks from Akavir, Redguard's cut cannons (source Michael Kirkbride), and also the aforementioned exploding Dwemer crossbow bolts in Skyrim.

It does not seem lore-breaking to introduce a flintlock style musket using black powder weapon to such a world, given the existing lore of ancient but highly advanced beings (the Dwemer), and many ruins where some of these ancient artifacts can be encountered.
Cyrodil and Imperial muskets use black powder obtained from Redguard sources.

WHAT THE MOD DOES
The mod adds a few different style muskets and blunderbusses to the world. They are all flintlock variants. Muskets can be smithed by an experienced blacksmith, and ammunition (black powder and musket shot or balls) can be easily created with spare parts obtained in the world.

You need the steel smithing perk, as many of the working components of a musket require a higher level of crafting ability than that guy in Riverwood can teach you.

If you add the optional "Ordo Legionilis Overhaul" file, the muskets will be carried by some Legionnaires and Penitus Oculatis members. I recommend using it alongside my other weapon mod, "Pistols (For travel in hostile environments). In fact the .esp is dependent on that mod.

WHERE TO FIND THE WEAPONS
As mentioned you will be able to craft some models at the forge, and if using the overhaul mod, will encounter them in the world, almost exclusively in the possession of Imperial soldiers. It is their technology after all.

TECHNICAL STUFF / WEAPON MECHANICS
The muskets use the crossbow animation, which is the best the game engine allows for. This is why the muskets are all a short varient. In order for the musket to function, you obviously need ammunition in your inventory.

CREDITS
Built on the work of ghosu with his "Project Flintlock" mod for Skyrim LE (never ported). I changed several feautures of the muskets (textures, size), and aspects of their functioning (new sounds, different impacts). Credit to ghosu for his incredible work.