Not that I have an extra nib, but I was curious — my Pelikan 140 nib fits into my Esterbrook LJ with no problems, ink seems to flow well. This also includes screwing on the cap. However, the converse doesn’t work — Estie nibs don’t fit the Pelikan barrel. 

The Pelikan 400NN nib is larger, and the difference is enough that I’m wary of trying to close a cap over it.