Sailing 3 September, "McCoy Reynolds" escorted ships via the Admiralty Islands to the Palau Islands. From 20 to 24 September she screened shore bombardment ships aiding the conquest of Peleliu by U.S. Marines. On 25 September, en route to join Task Force 57 out of Guam, "McCoy Reynolds" made underwater contact with a suspected submarine, and for 2 hours launched four depth charge attacks without results. At 0203 26 September, she picked up a contact on surface radar at about 9,000 yards (8,230 meters). Five minutes later it disappeared; however, at 0213 her sonar regained contact at a range of 2,500. At 0219 she launched the first of seven vigorous, intensive attacks with hedgehogs and depth charges on the target, probably submarine "RO-47". Four hours later, a violent underwater explosion was felt, and her lookouts spotted an oil slick which by noon covered an area of .