Hey Skinner,
I don't shoot a .375 H&H but I do shoot Trail Boss.
The Hodgdon web site recommends that you mark a case where the bottom of the bullet is when seated.
Fill to the mark with T.B. and weigh it, this is your max load!
70% of the max load is a start load.
Check the Hodgdon web site, Data page, Trail Boss Reduced Loads
OBTW, Welcome to the Fire!
Last edited by colodog; 06/25/12. Reason: add comment