Thread indexing on Luger Barrels Question

[Vlim]

Rich, it is an in-the-white barrel screwed into an unfinished receiver, both from the 1970s production. The metal part at the rear was retained until the last production steps were completed. It prevented the receiver forks from warping during production, and was finally cut away as one of the last machining steps.

These come from a retired Mauser staff member.