Ramshot tac is listed with many 50 gr. loads on their website.
Go to page 9, many loads using the Tac powder and 50's. Although the Speer 50's are not listed you should be able to start low and increase in small increments to max pressure. Use the load data for the Berger 50 GR FBHP's
I also have the new Nosler 7 load book, it lists tac with the Nosler 50 and 52 FBHP bullets : Tac 25min -27 max the accuracy load was 25.