Stock Assembly
The wooden assembly for a muzzleloading rifle is called a stock. At the base of the stock is a metal plate called the butt plate. At the front of the stock is another metal cup called the nose cap. This piece fits in underneath where the barrel will protrude. And where the barrel fits in along to top, there's a groove called the barrel channel.
Barrel Assembly
The barrel, through which the bullets pass, is fitted with another metal piece, called a tang, before it is fitted to the stock. At the rear end of the barrel is a breechplug. There's a protrusion here, like a button, in which the tang fits with. Together these pieces fit to the stock and function with the trigger assembly.
Firing Assembly
The trigger assembly is held into place with tang screws. Around the assembly is a lock and load plate and a trigger guard. On top of the barrel is the sights, which aid in aiming and firing the gun. The trigger assembly is typically simple on muzzleloading guns.