Are you sure that you are going to use 120 gr bullets? Barnes catalog only goes up to 115 grs in the TSX. But what ever one that you choose you need to pick up a reloading manual to get the load data and work up a load that is safe in your rifle. What is safe in my rifle may blow yours in two. Or at least freeze the bolt in the action.
The Barnes Reloading Manual # 3 lists 48 grains of RL 19 as the starting load with a velocity of 2791 fps and a maximum of 52 grains with a velocity of 3024 fps and this is with their 115 grain XFB bullet. I would start with a load of 50 grains with 3 rounds then 3 rounds of 51, 51.5 and three rounds at 52 grains. Watch for any signs of excessive pressure. Mainly the bolt being hard to lift to eject the spent case. Also check the case head for any brass flowing into the bolt face. This is a fairy fast way of getting the load that you want to shoot and you can do it with one trip to the range. With three rounds each you can check for excessive pressure and accuracy together.
Want a quick and inexpensive call for Moose? Take an empty 32 ounce coffee can, and make a small slit in the bottom, only about a quarter inch. Then, take one of those really big red rubber bands, the ones that go around big folders. Cut the rubber band to make one long piece.
Now, thread one end of the band and tie a knot on the outside of the can so it won't pull through. Cut the band off on the other side so it is even with the top of the can.
Now, wet your finger,...