The KwK 36 was derived from the 8.8 cm FlaK 36 anti-aircraft gun by adapting/modifying it to the limited space available in tank turrets. Parts of the KwK 36 were built to practically the same design as the 7.5 cm and 5.0 cm guns already used in German tanks. The breech ring was square in section and on a side. The breech block was of vertical falling wedge type and operated semi-automatically, meaning that after firing the empty cartridge case was automatically ejected, while the breech cocked itself and remained open, ready to receive the next round. The "L56" in the designation is a traditional measurement for artillery pieces. "L" refers to the length of the interior of a gun tube in proportion to the size of its bore, an important metric in determining a gun's relative performance for its bore size. The inside diameter of a gun tube is considered one caliber. The designation "L56" means the barrel is 56 calibers long, or 56 times 88 mm = 4,928 mm; almost. Thus, it is not an absolute unit of measurement; it is a proportionate one, and thus is rarely used while considering overall dimensions. Rather, it is used to denote how much velocity a gun will generate for its bore size. The longer the tube is in relation to its bore, the higher the muzzle velocity it can generate. A longer gun barrel allows the expanding gas from the shell's charge to act on the projectile longer than a short barrel, imparting it more velocity and force. For the Tiger II's 8.8 cm KwK 43 L/71, 71 times 88 mm is 6248 mm, over long. Shorter tubes are most useful for indirect fire, such as howitzers or infantry support. For anti-armour purposes using traditional solid shot, a long to very-long tube is needed, to generate the necessary velocity.
Performance
The KwK 36 was very accurate and high-powered, and its high muzzle velocity produced a very flat trajectory. This allowed its gunners a higher margin of error in estimating range. In British firing trials during the war, a British gunner scored five successive hits from at a target. Another five rounds were fired at targets moving at, and, although smoke obscured the gunners' observation, three hits were scored after directions given by the commander. The sighting system resulted in excellent firing accuracy for the 8.8 cm KwK 36 gun on the Tiger I.
Capability
The gun's performance was highly dependent on distance to target and type of ammunition loaded. For kinetic penetration, the speed of the projectile upon impact is crucial, and cumulative effect of air resistance decreases the velocity of the shell as the distance to the target increases. The accuracy achieved during controlled test firing to determine the pattern of dispersion gives a greater accuracy than the variation expected during practice firing on a range due to differences between guns, ammunition and gunners; both at precisely known distances. Due to errors in estimating the range and many other factors, the probability of a first shot hit under battlefield conditions was much lower than at the firing range. Observing the tracer from the first round in battle, the average, calm gunner might achieve the firing range accuracy shown in the second column with the second round fired at the same target. This gun used the same size 88 x 571R mm cartridge employed by the Flak 18/36/37.
