On 25 April 1943, 137 claimed a "probable" victory over an FW190 and on 15 June, the new C/O S/L John B Wray damaged another 190. Squadron Leader Coghlan had completed his tour of operations on 23 May and handed-over to Squadron Leader Wray, a highly experienced pilot.
The last Whirlwind operation by 137 took place on 21 June 1943, after which the squadron moved to RAF Rochford, Southend-on-Sea, to train in the use of the Hurricane IV. This aircraft could be equipped with both the 40mm cannon that had been successful against Axis armour in North Africa and with the new 3-inch rockets that would become synonymous with 137's ops. The rockets were still a relatively untested weapon and 137 spent June to July practising with the new ordnance.
In August, the squadron returned to manston for the second time and began operations with the cannon and rockets in conjunction with the rocket-equipped 164 squadron. The rockets were still officially a secret.
Rocket attacks were initially restricted to attacks on shipping to avoid the new weapon system being captured by the enemy. 137 kept six Hurricanes equipped with the 40mm cannon for attacks on land targets. The 40mm was not sufficient to deal with the latest Axis armour but were devastating against other motor-transport and would blast the boiler clean-off a train. The Hurricanes were equipped with two .303 machine-guns but these were of use in supplementing the ground-attack fire rather than for fighting enemy aircraft. The 40mm Hurricanes were not fast enough to engage enemy aircraft but the rocket-equipped Hurricane could regain it's performance once the rockets had been unloaded onto a target.
Their first rocket attack over land took place on 2 September 1943, when the two Hurricane squadrons attacked the massive lock gates on the Zuid Beveland canal in the Dutch Islands. This was a memorably hair-raising attack and the low-flying Hurricanes trailed back carrying pieces of telegraph-wire and branches plus flak-damage. John Wray's aircraft had snared a duck in it's leading edge. The duck was handed to the groundcrews for dinner! Sadly, four aircraft were lost in the operation.
In December, 137 moved to RAF Lympne where they engaged primarily in attacks against shipping.
In the same month, Whirlwinds became officially obsolescent. However, 137 pilots and crews consistently praised the aircraft and the early end to it's career owed more to production failings than to any lack of performance of the aircraft.