Take it over to Silberman Brown in downtown Seattle. He'll do the nib exchange for you if you want a B!
Thanks for the referral. I didn't state things well. I love the M and don't want to change it and normally I like B's in Jowo or Bock. It's closer to a B than then other M's so right in my sweet spot of what I like. So if some like likes a finer M they might want a F then this nib.