At 19:00 hours on October 12th after shelling and sinking the the 14,115 ton Emile Miguet the U 48 pursued and engaged in a gun battle with the 5,202 ton Heronspool shortly after midnight on the morning of the 13th. The Heronspool fought back with fore and aft deck gun forcing the U 48 to fire six torpedoes only one of which exploded. The Heronspool then sank. On the same day after two gun engagements the U 48 ran across the Louisianne a 6,903 ton merchant and preceded to shell her.
"At 08.14 hours on 13 Oct, 1939, the Louisiane, a straggler from convoy OA-17, was stopped with gunfire by U-48. After the crew abandoned ship, the vessel was shelled from 08.35 until 08.45 hours and sank ten minutes later."
http://uboat.net/allies/merchants/ships/64.html
one day later the U 48 preceded to Shell the 2,677 ton Seaton. The crew was then allowed to abandon ship and the U 48 torpedoed her causing her to sink.
So in 3 days the U 48 sank about 29,000 tons of shipping as result of having a deck gun. 21,000 tons was sunk directly by the deck gun. An 88 mm (3.47") gun with a magazine of 220 shells!
Maybee the deck gun is an uber gyro stabalized ray gun of death after all
