How did a depressed gun keep its cannonball in place?

How did the crew keep a cannonball in the bore when Koehler's gun carriage pointed downward?

They used substantial wadding and fired promptly once the gun was depressed.

Koehler's carriage allowed a gun high on the Rock to fire at targets below the usual horizontal line. That created a basic loading problem because gravity could draw the round toward the muzzle. Crews used a large amount of wadding to hold the ball and fired quickly after depressing the piece. The exchange adds the practical gun-crew procedure behind an otherwise abstract engineering innovation.