Is a 150 grain partition/xp3 ok to use on elk? I got a 300wsm but I know people use less grains from smaller calibers.

Absolutely.. Just nail him in the Heart! I prefer a little heavery bullet. I shot my first elk with a 30-30. and a 160gr. soft point bullet. So, it is all about placement!

It'll do. Even if you hit a little far forward you'll still break the shoulder.

TGH...
I also hunt and shoot with a .300WSM. The 165-180 grain bullets are the mainstay of this cartridge. Accuracy and knock down power seem to be better with the 165's or 180's. The BC's are better and a partition in 180 grain will kill an elk as far as you can shoot and shoot at MOA at 100 yds with good handloads. In my opinion, I'd save the 150's for whitetails and antelope and step up for the elk.
Good luck.

150 grains is more than enough. my brother and i used 140 grain boattails in his .270 many years ago for elk. Mine was slightly over 300 yards and took the top of the heart out while his was 120-125 yards and destroyed the liver. We found his bullet behind the elks eye.

Yep that'll bring an elk down, a guy i hunt with uses 150 High Energy partitions and hes shot moose and elk with them and he has a 7mm.

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!!

Skeeter, what's the deal with the speeds? Does the Tsx not expand as much? You seem to be quite knowledgable in this dept.

Ditto!

"The bigger the bait, the bigger the fish! "

Well bigger the bullet, shorter the blood trail. (lol)
Personally, I shoot the .300 WinMag and use 150's for deer, antelope, or bear. The 180's for elk. But 150;s will do the trick. Like they said, shot placement. I like to aom for the "high shoulder" shot myself.Folds them up like a wet card table! I've chased too many elk after shooting them through the heart/lung area.