The 300's there are about the same, the faster one is the Ultra though, so he is essentially wrong. The Ultra lacks the belt, has more case capacity and offers 100-200 fps more speed for a given bullet weight than the Wby.
I'm using RL22 and RL25 both with great results in my 300 Ultra. I'm getting about 3250 fps with RL22, and 3300 fps with RL25 using 180gr bullets. Accuracy is great just below max load with both. Best bullets in mine were 178 A-Max, 180 Scirocco, 180 Ballistic Silvertip so far.
Start with about 88-90gr with RL25, 96gr was max.
Start with about 80-82gr with RL22, 88gr was max.
I've had good luck with a max load of 86gr of RL25 using the 220gr SIerra Match King too.
All these loads were tested with longer overall lengths, and your max loads may be a grain or two less if seating bullets deeper to fit in the magazine, mine were single fed to touch the lands.
Good luck and have fun reloading for it, it will be very rewarding, and give you lots more ammo to shoot for your hard earned cash spent on it.
If you have not educated yourself about the reloading process, which is fairly simple once you get the hang of it, BE SAFE for starters, and the rest of your life doing it.
There are some things that can kill the most edjucated reloader if he isn't carefull all the time while one's loading.
A couple things to never forget:
1) Don't ever use a powder that you have not opened the seal on and know **** dood and well, without a doubt, that it's the powder contained there in.
2) Never set more than one can of powder on the bench at a time, so they don't get mixed up with what's in the dispensor. Lable on masking tape what's in the dispensor and stick it on the dispensor if you need to. DON'T GET MIXED UP! If you're unsure of what's in the dispensor at any point, get rid of it and don't take the chance using it by guessing!
3) Don't mix bullet weights up accidentally, weigh what you're loading first to make sure it's what's on the box!!
4) Double and triple check charge weights with MORE than one manual to verify your loads, no matter where you get the info from... get a concenses, start low and work up carefully to find the max load in YOUR gun.
5) Always make sure you use the right load data and don't get mixed up, double and triple check... have no doubt.
6) Visually make sure you have powder in every case before you seat a bullet into any them. Anything that didn't sound, or feel like a full power load when shot, be aware and don't fire another round until you make sure the barrel doesn't have a bullet lodged in it from a primer alone pushing the bullet down the bore... it can and does happen, and is detrimental to your health to say the least. If you make sure and visually determine a case didn't get skipped when dropping powder in them, it shouldn't happen, so long as you use an appropriate primer.
7) A change in lot #, any component or OAL should flag you to reduce the load and work up agian, as these things all can affect pressure.
I'm sure I left out a few things, so be carefull, don't get complacent, take your time and you should learn it all quickly.
Welcome to the board.
Lots of knowledgable reloaders here if you have questions along the way too.