I'd be looking to the same bullets in the 180gr bullets for elk or moose in the 300wsm.
BTW, comparing different calibers and similar grains doesn't tell the whole story, as their Sectional Density is different and should be at least factored into the equation for abetter comparison.
Ie (SD's for examples given in the post):
.308/150gr = SD of .226 (300wsm)
.277/140gr = SD of .260 (270 win)
.284/150gr = SD of .266 (7mm rem mag)
SD not the only thing to consider but if bullets of equal construction are used the .308/150 is the weakier of the 3 examples given.I am not saying it won't work as the Nosler partition is a great bullet but at the speed the 300wsm will spit the light for caliber 150gr bullet out I'd prefer to error on the side of caution. If I feltthe need for a light for caliber bulletI'd go to a Barnes TSX instead.
Sure shot placement is key butit doesn't alwayspan out with a textbook broadside shotin the real world and of course the ever present human factor is reason enough to consider at the very least a small insurance plan!!Elk aren't bullet proof but they are much different then deerand if you wanting 1 load for everything I'dsay be overkill on the thin skinned gamevsthe other side of thingson the thick skinned game.
Just my 2 pennies worth!!