The Jr. Gent is a #5 Jowo medium nib. If you want something bolder then get a broad tip or you could try a flex nib. I have liked the nibs from Pen Realm, select his free tuning. I have also used Goulet branded and Edison nibs from Goulet Pens. Not sure the size of the Atrax nib. If it looks larger than the Jr nib then it is a #6 Jowo. If it looks the same size it is a #5. The nib size will not change the line width. Have fun, you are heading down the rabbit hole of fountain pens. You can also try stub and italic nibs. Steel nibs are not that expensive so get several and try them.
The Atrax is a #5 size nib, I have two of them sitting on my desk right now.
It is not a Schmidt, I have a few Schmidt #5 and the housing threads don't match up.
I suppose it could be a Bock or Jowo, but I don't know as I don't have any of their #5 size nibs to compare to.
I agree Eric (
@Bope) either way, give Kirk Speer at
Pen Realm a try. Go to the Contact tab and send him a note.