I have an old Speer #10 manual that I purchased back in 1979. For the .270 Winchester with a 130 gr. Speer bullet, a Max load of 62.0 gr. of MRP is listed as producing 3071 fps muzzle velocity out of a 24" barrel; 60.0 and 58.0 grains are shown as producing 2998 and 2892 fps respectively.
For the 150 gr. bullet, they show 58.0 gr. Max at 2831 fps, 56.0 gr. at 2742 fps, and 54.0 gr. at 2622 fps.
I would suggest starting with the lighter charge and working your way up in half-grain increments while observing all standard safety precautions until you reach your rifle's max load and then backing off a couple of grains for a hunting load. MRP is known as an old magnum cartridge, heavy bullet, slow burning powder. Therefore, you may want to consider a magnum primer for consistent ignition.
Hope this helps.