Rotring Core question

I bought one a few days ago, and I'm not crazy about the ink flow. It's
a bit dry, which makes it a bit scratchy too. I've ordered a converter
for it, and will put different ink in it, as well. (I bought the Rotring
cartridges.)

Is it reasonable to expect anything different? Is their ink not that
good? This is the only pen I have that uses cartridges, so I don't know
if that will make any difference.

Any thoughts or similar experiences?

Bob