I suggest you address your query to ACWSA and ask them. It's their rule and they would be the ones to provide an explanation, not us.
There really isn't any rule on to clear a gun that does not fire, only to flood the bore and pull the gun off to the side to be cleared after the competition is over.
Possible methods for clearing guns assuming the projectile is seated properly:
1. Dribble some powder into the vent, enough to blow the projectile out of the bore. I had to do this once and the projectile came out and not the powder charge. I flooded the bore and removed the charge with a worm.
2. Projectiles that have enough windage may roll or slide out of a barrel that is tipped down. This works very well with round balls. I have had a cannon ball roll out simply by depressing the muzzle, which gets a good laugh if you didn't want it to come out. Difficult to do with large guns as you may have to lift the trail quite high.
3. Co2 injected through the vent. Bottles are not usually available at most events.
4. Flood the barrel and try to hook the projectile in some manner to pull it from the barrel. I haven't any experience with this method and tools needed would depend on the shape of the projectile and the material it is made of.