What type of muzzleloader uses the #11 Percussion Cap as its ignition source?

The #11 percussion cap is specifically designed for use with caplock muzzleloaders. In this type of firearm, the cap is placed on a nipple that is directly attached to the firearm's action. When the trigger is pulled, the firing pin strikes the percussion cap, igniting the primer inside, which in turn ignites the main charge in the barrel. This ignition method is known for its reliability and rapid firing capability compared to earlier methods.

Flintlock muzzleloaders rely on a flint striking a steel frizzen to create sparks that ignite the powder, making them incompatible with percussion caps. While inline muzzleloaders can also use percussion caps, the term "caplock muzzleloader" encompasses all firearms utilizing this ignition type, including inlines. Therefore, while inline muzzleloaders employ the #11 percussion cap, the most accurate answer that highlights the overall category of firearms that utilize this specific ignition system is the caplock muzzleloader.