muzzleloader is the ACTION PART.

The Action part of a firearm is the part that concerned with ammunition loading and shells ejection. It’s the guts of the gun. The action part fires and unloads the cartridges. It is seen as the heart of a rifle. The action part is composed of the bolt, hammer and it is usually at the middle of the rifle. There are different types of firearm action and this include

Lever action is manual firearm type; it uses a lever to load cartridges, some lever actions have a tubular magazine.
Bolt action is manual firearm type; it is simple and easy to use. However, some bolt action rifles are repeaters which imply they have additional cartridges in a magazine.
Pump action is a manual firearm type; this manual type of firearms is often called slide-action firearm. An individual must slide the forend, both back and forth ways to use this type of action.  other types of action includes, semi-automatic action.
The lock on a muzzleloader performs same functions with extra safety measures to stop accidental / unintended shootings.  The muzzleloader is divided into three parts, which are the lock, stock, and barrel.