In June of 1863, the Royal Bavarian State Railways (K.Bay.Sts.B.) placed the first 2-4-0 express locomotives into service, the new class B VI. In many respects they were the same as the predecessor model class B V such as the heating surface, the grate area, cylinders, etc. The improved double outboard frame and the Bavarian version of Stephenson valve gear were also approximately the same. One essential difference was the driving wheel diameter, which initially was 1,600 millimeters / 63 inches, on later deliveries 1,620 millimeters / 63-3/4 inches, and some even were 1,640 millimeters / 64-9/16". A total of 107 units were delivered to the Bavarian State Railways in two production runs by June of 1871. The 57 steam locomotives delivered from June of 1863 to February of 1867 in the first production run only had a boiler pressure of 8 atmospheres / 117 pounds per square inch, a dead load safety valve on the dome that had a watering can casing, a simple protective roof for the engineer's stand (later also with an all weather roof), a steam pump, and an injector. The smoke stack was just a stack with a bell-shaped crown, cylindrical stacks, or pear-shaped stacks.
The second production run of 50 units was considerably more advanced: The boiler pressure had been raised to 10 atmospheres / 147 pounds per square inch. The necessarily higher boiler weight also resulted in improved traction. The weight increased from 22 to almost 23 tons. The weather "umbrella" that was totally insufficient for the locomotive crew was replaced by a short but complete engineer's cab. The pumps had disappeared since the injectors had proven sufficient in operation. A funnel-shaped smoke stack of a moderate shape lent a certain degree of standardization and had been preceded by different experiments with other stack shapes.
Both production runs were designed for either coal firing or peat firing. The coal-fired locomotives had a three-axle open tender, while the peat-fired units were equipped with a newly designed, three-axle enclosed tender with smooth walls. Naturally, there were several rebuilds during the long service life of the class B VI in which primarily the units of the first production run were brought up to the level of the second production run.
After being placed into service the class B VI locomotives were assigned to the greatest part of the express train service at that time over a period of ten years. However, their "swiftness" was kept within limits, because the speed reached was just barely more than 60 km/h or 38 mph. When more powerful steam locomotives appeared starting in the 1890s, the B VI gradually moved down into lower levels of service. The first few units were retired starting in 1895.
In closing it can be said of the class B VI: They were indestructible, long lived, and well proven units of which quite a few reached a service life of over 50 years.