I own a Ruger M-77R tang-safety .300 Win Mag I bought new in 1975. My favorite elk and large deer load for it is 74.0 gr of IMR-4831 with a 180 gr Nosler Partition and a CCI LR Mag primer in W-W brass. This is a MAX load and you need to work up to it. I get around 3100 fps out of this load and less than 1" groups. I'm gonna try H-4831SC when I shoot up my present supply of the loads with IMR powder. I used to load this with a standard partition for in the chamber and then the Protected-Point partitions in the magazine, but I found that out to 400yds, I couldn't tell the difference in the POI between the two, so I load the Protected-Pt partitions exclusively now.
If you want to tear a whitetail nearly in two, try the 165 gr Hornady SST or 165 gr Nos Ballistic Tip and 79.0 gr of RL-22. This gives over 3300 fps in my rifle, but again, it is a MAX load. Approach carefully! If you shoot the deer in the shoulder, it makes a huge mess but will blow all the way through. Punching through the ribs behind the shoulder isn't nearly so bad, and doesn't tear up too much meat.
I honestly think that the 200gr Partition pushed with 71.0gr of IMR-4831 could probably do a "Texas Heart Shot" on a bull elk, but I wouldn't try an iffy shot like that. If I was elk hunting in grizzly country, that would be load I'd carry, if I used my .300.
Note: You can back off of all of these loads a few grains and still exceed .30-06 velocities, but with less recoil and LOTS less muzzle blast than the max loads. The .300 Mag Rugers with the red butt-pads really are vicious kickers.
I've also shot some 130gr Speer Hollowpoints out of my .300 that did amazing things to groundhogs, coyotes and feral dogs.
Also, you can adjust the factory trigger to a very good pull. It is adjustable for weight of pull, sear engagement, and overtravel. I bought a new trigger return spring from Midway or Brownells that allows adjusting the pull weight all the way down to around a pound or so, and really like it. I keep mine set to 2 1/2 lbs. But you can achieve the same thing with the factory spring, and if it won't go that low, you can CAREFULLY trim it to achieve the desired weight of pull.