I know for a fact that a rubber mallet was being used against the action to see if it would fire. The reason I know is that an importer known to me told me he saw it being done when he was collecting firearms.

It was only then he realised that a number of shotguns he had returned to the makers for dings in the rib were actually caused by Customs, my understanding is they settled up on damages, not sure if the mallet is still in use.