Final P_orb versus initial P_orb for all binaries investigated with M₂ = 1.4 M_⊙, M_NS = 1.3 M_⊙ and a magnetic braking index of γ = 5 (cf. Fig. 2). The arrows at the bottom indicate the initial P_orb of the four highlighted systems. Circles represent solutions, i.e. systems which detached while situated inside the grey shaded region that marks the location of the observed MSP systems with P_orb = 2−9h. The values of initial P_orb for these systems are confined to an extremely narrow interval (the orbital period fine-tuning problem, cf. Sect. 4.2.1). Open stars represent converging systems (which do not detach) and for which we ended our evolutionary calculations before reaching P_min. The vertical dotted lines represent P_detach, P_UCXB, and P_bif – see text.