Wadding

Wadding is a disc of material used in guns to seal gas behind a projectile or to separate powder for shot.

Wadding can be crucial to a gun's efficiency, since any gas that leaks past a projectile as it is being fired is wasted. A harder or more carefully designed item which serves this purpose is often called a sabot. Wadding for muzzleloaders is typically a small piece of cloth, or paper wrapping from the cartridge.