This doesn’t affect the performance of the pen or my thoughts of this pen, but one thing with Kaweco sometimes can: The nib. The brand is known for sketchy quality control on their steel nibs, especially with what is referred to as a Baby’s Bottom. This causes skipping and poor line performance, and has plagued Kaweco for years. I almost never have a problem with my Kaweco nibs because I generally order them with extra fine nibs. You hear more reports of this issue with medium or broad nibs.
I’m happy to report the extra fine nib on my Steel Sport is perfect, but again, your mileage may vary.
To fill the Steel Sport, I used the Diamine 1864 Blue Black ink cartridges. I find Kaweco’s inks to be a little washed out, and there are a ton of short international cartridges on the market that I prefer.