My favorite for my 7mm Mag is a 160grn Speer Mag Tip but since they are discountinued and I run out, I will switch over to the Grand Slam.
I have the .264 Win Mag, .270WSM, 300WSM, 7mmRUM, 300RUM, and 338 RUM, and shoot and hunt with all of them regularly and have has some limited use the the 7mmWSM as well. All are great calibers and any would be a big step up in ballistic performance from the .270winchester (especially with 150s). I would consider any of the WSMs and the smaller 2 RUMS pretty tough to beat for an all around north american and african plains game cartrige if you could only have one. Unless you are a handloader, I wouldn't recommend any of the 6.5's just because ammo can be a little tougher to find. The .264 Win Mag pushes a 130 accubond about 3150fps which some would consider a little light for elk and other larger north american game, but if it's deer you are after and you handload it's worth serious consideration. Along with the ballistic improvements you will also notice a step up in recoil, especially with the RUMs. The RUMs all require a muzzle brake to be tollerable, and the WSMs are a little more pleasant to shoot with a brake as well. The other big difference between the RUMs and the WSMs is the barrel length required to achieve maximum performance. The RUMs will need a 26" tube, whereas the WSMs can get by with a 22-24" tubes. I probably like my .270WSM with 130gr E-tips at 3343fps the best. Hope that helps.
In my .300 Wby I use Nosler Partition...180 grainers. Shoots really well with Reloader 25 powder, get 1 minute or less groups. My deer rifle is 25-06 using Sierra 117 bt bullet and in the same gun for antelope I use a 100 gr Sierra bt.
I recently had Leupold set up a custom elevation knob for my loads for the .300. Just finished all my testing and I am very pleased. It is zero'd at 200 yds which I left at 3/4" high @200. Shoots exactly the same (3/4") at 300, 400 & 500 yds. Going to try some at longer ranges next week. I guess I'm old fashioned as I am using the same bullets I have been using for the last 30 years or more. My motto has always been...If it ain't broke, don't fix it!
Cowboy Action Shooter; Endowment Life Member-NRA
The Original Rocket Scientist-Retired
"My Father always considered a walk in the mountains as the equivalent of church going."
Found a new favorite for my .338 Mag
Hornady Superperformance 185gr GMX
Controllable recoil, hard hitting and flat shooting. I smoked the 4" steel target 5 times in a row at 300 with them. Can't wait for elk season.
"Courage is being scared to death, but saddling up anyway."
Hunting camp coffee isn't complete until you chew the last drink.
7-08 with Hornady SST 139 grain, man i love this caliber.
7x57 with the Hornady SST, my son knocked down a nice 5x5 bull this year with this one.
Weatherby 257 Magnum
My favorites and best shooting are:
140gr Accubond and/or 140 gr Partition in my .280 Rem
210gr Partition in my 338-06
Hornady 100 gr. SP in my .257 Ackley Improved. However, it's all about bullet placement, not the brand of bullet. As long as the weight is appropriate for the game, the bullet placement is more important.
New to me is RWS 7mm 177gr. This stuff shoots paper better than anything I have shot. My oldest gun is a Rem 700 7mm and it likes the RWS.
180 gr. Barnes TTSX or TSX in Rem. Mod. 700 Stainless. 300 Ultra MAG. Very accurate combo with 100.o grs. Hogdon Retumbo.
140 gr. Barnes TTSX or TSX in Ruger MK II Stainless . 7mm Rem Mag. Best load with 70.0 grs. Alliant RL 22.