What could cause a sudden, complete blockage in my flintlock's White Lightning vent liner that prevents water, air, or a vent pick from passing through?

A complete blockage in a White Lightning vent liner that resists water, solvent, and a vent pick is almost always caused by a compressed plug of black powder residue, rust, or patch fibers forced into the internal cone of the liner. Because the White Lightning liner is coned on the inside, debris can act like a one-way valve or wedge tightly into the narrowing passage. To clear it without removing the liner, try using a small, stiff wire (like a guitar string or piano wire) from the outside, or use a breech-flushing tool to apply hydraulic pressure from the muzzle. If the blockage is rusted or seized solid, the vent liner may need to be drilled out and replaced.