MSS SP-75: Specification for High-Test, Wrought, Butt-Welding Fittings
as you may consider through name of MSS SP-75, it is for wrought fittings,i.e. forged/formed.
you may use the design code of your piping system to make such a welded branch connection and make the dimensions of the Tee (C, M) as per MSS SP-75 TABLE 7.
Regards,
A. Bohlool