Trail Boss is the easiest loading powder for reduced loads. Full charge is full to the bullet's base. Lightest load is 70% of that.
Expect vel. to be just over 1,300fps in a mildly bottle necked case.
Straight cases usually produce in the 1,100fps range.
Expect pressure to he in the 22,000 psi range judging/extrapolating by published data from Accurate Arms and Hodgdon some years ago.

Pardon me. Just reread and see Markorov bullets.
Oh well. Same powder, same 70% capacity to 100%. Will likely be 8 to 12gr. & be in the 1,500fps range. Just an estimate.