Do you mean the Jaguar/Junior/Rangers from the 1950s onward?
Because they kept making the Mk3 until the 70s, made the 8-9 ft-lbs Falcon in the 60s, and replaced the Mk3 with the Mk3-level power Osprey and Hawk, and not long after the Vulcan/Viscount/Tracker which were proper 10-14 ft-lbs rifles.