I don't have my reloading notes in front of me but I can remember some of my favorite 350 Mag loads out of my Ruger MK II. I have used both IMR4320 & H322 with the 220 Speer FP bullet. I know both loads were a grain or 2 under book max and with either load I was achieving about 2,560 fps. Accuracy was just over 1" for a 3-shot group at 100 yards. I have used this bullet for deer hunting and it has worked very well.
I also tried just a few reloads using TAC and the Barnes 200gr TSX. I've thus far achieved around a 1.5" 3-shot 100-yard group but I've not yet played with the seating depth. I was using 1 grain below the Barnes book max and the average MV was around 2,880 fps. Though Western in an e-mail told me that TAC works well with standard primers, I thus far have only tried Federal Match Magnum primers in my reloads. I'm confident that, if I ever get the time, I should be able to get better groups with the TSX by adjusting the seating depth (though 1.5" group at 100 yards is really all I need). I've yet to take any game with the 200 gr TSX.
Good luck.
