In the line of 4-8-2 locomotives designated U-1 by the Canadian National, the U-1f was the last class that followed in 1944, 14 years after the U-1e. This did not only have a larger boiler and higher pressure, an increase in power was mainly achieved through internal streamlining. Like the U-1e, it had cylinders with a diameter of only 24 inches instead of 26 thanks to the higher pressure. A part was fired with oil and a part with coal.

Due to their cover on the smokebox door, they got the nickname “Bullet Nose Betty”. They were used for express passenger and express freight services. With a driver diameter of 73 inches they could run fairly fast, but some claims of 125 mph (201 km/h) have to be questioned. Number 6060 was preserved and has run in preservation over several periods. The last time it was running was between 1998 and 2011. Today it is owned by the Rocky Mountain Rail Society and currently under overhaul.