What does "in-line" mean in the context of muzzleloaders?

In the context of muzzleloaders, "in-line" refers specifically to a design where the ignition system, typically utilizing a percussion cap or a primer, is aligned directly with the barrel. This design allows for more efficient ignition by ensuring that the flame produced by the ignition source travels in a straight line into the barrel, igniting the powder charge quickly and consistently. This alignment also helps maintain a streamlined firearm profile, making it easier to handle and aim.

The significance of this design choice means that in-line muzzleloaders often feature improved accuracy and reliability compared to traditional muzzleloaders with other ignition methods, where the ignition source may not be directly aligned with the powder. This advancement has led to a surge in popularity among hunters seeking modern muzzleloading firearms that offer the advantages of more contemporary technologies while retaining the unique characteristics of muzzleloading.