主题：【原创】激战，在中国的天空 – 日本所存抗战时期老照片选 一 -- 萨苏

虽然被冠以20 mm antiaircraft-gun M/23 Semag-Oerlikon之名，但实际上这炮本身和Semag没什么关系。如果说一定要有关系的话，那是因为这门炮用的是Semag设计出来的20X99RB弹（同样也写做20X100RB或者20X101RB）

这门炮的正式名字应该是“Semag-Oerlikon Type L”是厄利空FFL的前身。

“As described in "Rapid Fire", the first API Blowback cannon was the 20mm Becker which saw German service, as both an aircraft and an AA gun, at the end of the First World War. SEMAG bought the design and produced a more powerful version firing a longer cartridge (the Type L). Oerlikon then took over and introduced the Type S, firing an even bigger cartridge. By the late 1920s, the range consisted of guns built around three different 20mm cartridges; in order of increasing size and power, the Type F (70mm case length, later increased to 72mm), the Type L (99mm, later 100mm or 101mm in the Japanese Type 99-2) and the Type S (110mm). Their muzzle velocities were respectively around 600 m/s, 750 m/s and 820 m/s. These three ranges continued to be developed together.

In the mid-1930s, all three guns were offered in improved versions, suitable for aircraft use. They were known as the FFF (usually just FF), FFL and FFS respectively. ”

（Anthony G Williams）

从上面这段话中，我们可以发现，在厄利空著名的三大系列：FFF（通常就写做FF），FFL，和FFS之前，厄利空还有个不出名的“老三大”系列：F，L，和S。这三个系列诞生在20年代早期（我想应该是在1924），但并没有得到推广和实用，而更类似于技术验证或者实验品。

至于你给的联接中提到这些炮来自Semag，我想那是因为它们是Semag工厂生产的。正如我之前说的那样，Semag在并入厄利空后，依然有自己的名字。它是作为一个分厂而继续生产原Semag设计的武器和厄利空的武器的。