 Fredericton was armed with one 4 @-@ inch ( 101 @.@ 6 mm ) gun forward and a 2 @-@ pound ( 0 @.@ 9 kg ) pom @-@ pom gun mounted aft . Two Oerlikon 20 mm ( 0 @.@ 8 in ) cannon were mounted on the bridge wings for air defence . Depth charges , which were rolled from the stern through two ports or thrown from four launchers aft were used for anti @-@ submarine warfare . Later in the war , she was outfitted with the more effective Hedgehog depth bomb throwers . 
