Her shakedown completed shortly after the middle of May, "William T. Powell" sailed for Charleston on the 18th. She met SS "Willis A. Slater" off the sea buoy to Great Sound that day and escorted the merchantman on her northward voyage, patrolling 2,000 yards ahead. Leaving "Willis A. Slater" off Charleston, "William T. Powell" put into port on the 23rd and, from 24 May to 6 June 1944, underwent post-shakedown availability. During the overhaul, the ship received four 40-millimeter Bofors guns, replacing the bank of torpedo tubes, to give the ship a more potent anti-aircraft battery.