At 14.12 and 14.13 hours on 3 Feb 1943, U-255 fired torpedoes at convoy RA-52 about 600 miles northeast of Iceland and observed two hits on one ship after a running time of 1 minute 50 seconds and heard one further detonation after 3 minutes 20 seconds. Reche reported the Greylock sunk and claimed a hit on another freighter of 5000 GRT, but this can not be confirmed from Allied sources.

Lookouts on the Greylock (Master Charles Herbert Whitmore) spotted a torpedo in the smooth seas and broad daylight about 300 yards off the port side. They tried to evade the torpedo, but it struck between the #5 and #6 holds, creating a large hole below the waterline and also locking the steering gear. A second torpedo missed the bow by 75 yards. The ship immediately flooded and took a starboard list. 15 minutes after the hit, the ten officers, 26 crew members, 25 armed guards (the ship was armed with one 4in, one 3in, eight 20mm and two .30cal guns) and nine passengers (three of them survivors from the Panamian freighter Ballot, which had been bombed and sunk on 25 Dec 1942) left the ship in four lifeboats. A British escort ship shelled the Greylock, causing her to sink stern first at 14.30 hours. The most men were picked up by HMS Lady Madeleine (FY 283) (T/Lt W.G. Ogden, RNVR) and HMS Northern Wave (FY 153) (T/Lt W.G. Pardoe-Matthews, RNR) and landed at Belfast and Gourock. Four crew members were picked up by HMS Harrier (J 71) (Cdr A.D.H. Jay, DSO, DSC, RN) and taken to Scapa Flow. All the crew came together in Glasgow and were eventually repatriated from Liverpool.