what nose cone ?

What nose cone to use or I/D for Estes 3.0 od tube ?

BMS sells a PNC-300K or a balsa version of it, Mercury Engineering sells the same cone, as does Apogee and eRockets iirc. The ID of Estes 3" airframe is 2.93" and is available from Balsa Machining Service in 34" lengths along with 4" and 6" couplers and full 34" lengths of coupler stock. The nose cone is slightly longer than the Big Daddy/Leviathan nose.
BMS also sells a 3" elliptical nc for the T300 airframe (BMS's designation for the Estes clone 3" tubing).

10-4 - thanks

The PNC-300K is a slight upscale of the Estes PNC-80K.