What was the point?

[Kohaku2416]

After i got offline last night and was getting ready for bed, i began to think of this. What was the point of the german navy having Lugers with a six inch barrel? I mean why didn't they just use the standard 4inch Lugers. Was it because the navy lugers give more accuracy or what? Same with Artillary crews and the ARtillary Lugers, what was the point on having a huge barrel.