What primer is used for caplock muzzleloaders?

Caplock muzzleloaders utilize percussion caps to ignite the powder in the firearm's pan, which is why the #11 percussion cap is the correct answer. This type of ignition system relies on a small, metal cup filled with a sensitive explosive compound. When struck by the firing pin or hammer of the firearm, the cap detonates and sends a flame through the nipple to ignite the powder charge in the barrel.

The use of the #11 percussion cap is common among caplock muzzleloading firearms due to its reliability and effectiveness in creating a quick and consistent ignition.

In contrast, other options like FFFFG priming powder and flint are related to different types of ignition systems. FFFFG powder is a fine grain black powder used for priming in flintlock firearms, not for caplocks, while flint is used in flintlock mechanisms that create a spark to ignite the powder charge. The 209 muzzleloader primer is specific to modern inline muzzleloaders and is not compatible with traditional caplock systems.