Can you explain a little bit better the term "nipple barrel", I can't recall ever hearing that term before.
Do you mean the tit the cap is placed on? Or are you referring to the drum, the part that the nipple is screwed into? IIRC, that is going to be somewhat difficult, as CVA does not encourage removing that part, and I think it is not available. The barrel might have to be returned to CVA for repair. Not to say a competent machinist cannot remove it and fashion a new one, just saying it can be a PITA.
John