My 7mm shoots 175 grain Federal Premium Trophy Bonded Bearclaw very well, so I started with those in 180 grain for the 300 wsm T3 Lite, but the best I could do was a two-inch group. Switched to Winchesters (I forget the bullet, but it was their premium (silver-tips?), also in 180 grain) and groups shrunk to 1" to 1.25". Then tried Remington Sciroccos (also 180 grain), and groups went sub 1-inch. I'm currently in the process of buying the stuff necessary to do my own handloading, but have not done any experimenting with that yet to be able to tell you about.
I'm two for two on hunts with the 300, shot a barbary ram and muley buck with the Scirrocos. The ram was running directly away from me with only the back of its head visible at a 100 yards, and I made what I consider to be a pretty 1ucky one-shot kill when I drilled it through the back of the neck. It was running off a hill and disappeared completely by the time I recovered from the recoil. I went running down the hill after it to see if I could get another shot at it once it was at the bottom of the hill only to be completely surprised to see it laying dead as a doornail where it dropped in its tracks.
The buck was standing broadside at 40 yards. I saw it flinch at the shot, but it didn't otherwise move, so I shot again. On the second shot it stumbled forward down a hill about 40 yards before piling up in some sage brush. When I got to it both bullets struck within an inch of each other and were complete pass throughs with small exit wounds. The buck was dead after the first shot, but after seeing that, I think it might be too much bullet for a deer-sized animal at that range. I intend to experiment with some lighter bullets for deer-sized game. If you find something that works for you, please let me know.