r/rOtring

Combining a new 600 Ballpoint with a Caran Dache Rollerball G2 Refill

I was carefully taking apart a bunch of pens I’d thrifted off of Vinted and somehow the nib unit of one of the rapidographs has gotten stuck in the bottom of the body I was using to detach it; I don’t remember even screwing it tightly at all but it’s well and truly stuck. Anyone have a clue how to help? I don’t have any specialised kit but I’m about to try giving it a very warm water soak.