Do all muzzleloaders only have 1 barrel?

No, not all muzzleloaders have only one barrel. While many traditional muzzleloaders are single-barreled, there are also double-barreled muzzleloaders available, which can have two barrels either side-by-side or stacked. Additionally, some modern muzzleloaders may feature multiple barrels or interchangeable barrels to accommodate different calibers or purposes.