When baked-bean cans became naval projectiles

Were baked-bean cans really loaded into a naval gun and fired at an Italian ship?

Yes; after ammunition ran out, cans were fired to preserve the appearance of continued attack.

Baked-bean cans were loaded into the gun after conventional shells ran out. They were improvised projectiles rather than a serious substitute for ammunition. Their purpose was deception: continued impacts and firing could persuade the Italian opponent that the attack was still under way. The episode shows how a crew might use almost any available object to sustain an operational bluff.