No sure what animals you plan on hunting but I am gonna agree with bearguide here, the 300 RUM is a beast and should be feed accordingly I'd opt for the 180 or 200 grain TSXs if thats the type bullet you are looking at. You'll get a better BC and more knock down. I am of the mind the 165 grain is more designed for the likes of the .308 and 30-06, but if you wanted a laser beam trajectory out to 300 yards with that RUM the 165s well certainly do the job.
I can only vouch for the 7mm, but I had good luck with accuracy on the 150 Barnes X in my Sako. In fact, great accuracy (3-shot, 0.75" w/ SD 0.25"). I sold the rifle and the new Weatherby wouldn't shoot them well, so I don't anymore. As far as performance, they always did well on big deer for me if I made the shot.
I shot the 168 gr. TTSX loaded with 94.5 grains of RL 25 and had great success with them out of my .300 RUM. I have since switched to a 175 gr. Berger that surprised me by how well they grouped. I assumed they would be all over the place because of the hollow point. The Barnes TSX I first tried would not hold a group better than 1.75" at best and I mistakenly put the blame on the hollow point. I am in the process now of loading up some 175 gr. Barnes LRX rounds to compare to the Bergers.
On game performance, the Barnes 168 did fantastic, the Berger also did great this last year, but I still have more faith in the construction of the Barnes when it comes to heavy thick skinned game.
each company calculates their own bc/ barnes claimes theirs is the most accurate and is calculated at different ranges. published bc of the berger's show the higest bc. the bergers seem to group better and are more consistant if you weigh each slug. i have never used the berger on game, just experimenting with loads to see how they shoot. i am shooting 190, and 185s with rl 22. i am getting 3300 fps at 7000 ft out of my 300 wby.
I used to shoot 168's out of my RUM. They were cooking along about 3500 fps. Shot well, and very flat. I have now gone to a much heavier berger and slowed them down significantly. Kind of fun but they were hard on my gun. It's getting re barreled right now. Recoil was the big positive. I have really grown to appreciate the wind bucking abilities of high bc's and 168's don't have them.
No Barnes here. For my hunting,with the rifles I have on hand,conventional bullets are just fine. Easier to develop loads with to boot. I don't have to seat them a 1/16" off the lands to keep the preasure down either. Oh I tried to come over to Barnes,without going into a bunch of detail at this time,their customer service bites. The last few correspondences with good old Ty over at Barnes were less than productive. I guess they are doing well enough now that they don't have to take care of the occasional individual problem. That's fine I guess. Monolithic bullets aren't required by law yet,and there is always Hornady should I get the urge to go there again. Which brings to mind a question I'll ask in another thread so as not to high jack this one. If I can't kill all the game I pursue with my 300 Ultra. Loaded with 180gr to 200gr Partitions or AccuBonds. At ranges that I can comfortably call my maximum. i guess it's time to dig the bow out again. No offense to my fellow hunters that have had good luck with Barnes. You are all my brothers from another hollow,but Barnes pissed me off.
If I had to choose a "premium" bullet for a 300 it would be a nosler accubond, 200 grains. I still prefer a 180 gr winchester power point, call it old school, but they group really well and I can buy twice as many of them for the same price.