Convoys had to deal with surface raiders on more than one occasion in WWII. One never knew when smaller DD types might have to take on more capable warships. the similar IJN Matsu class escort ships carried four 24 in. long lance torpedoes in a single four-tube mount for that reason. DEs and RN sloops etc were also escorts for CVEs in H/K ASW TFs. There were occasions to try and torpedo a surfaced submarine but I don't think it ever worked, particularly against the agile type VII series U-boats.
Most ship designs of WWII had been worked out before the US Army put the 90mm M1 into production, not that there was much interservice liaison and cooperation in any case. USN 3"/50 had a capable AP round, filled with explosive in the 1930s and given the army M66A1 base fuze. The HC ammunition also had some AP characteristics, esp. when the PD fuze is set to delay.
All rounds for the gun were 5.9kg, with MV of 823 m/s [2700 fps] so penetration would be superior to US Army 3-inch ammo; Rich has some details on this, maybe with penetration figures, which might be found in Campbell, Naval Weapons of WWII.
Edited by Ken Estes, 20 May 2017 - 0102 AM.