With the 200 gr AB, RL-33 is a nice load in the 300 RUM as it fills the case (103.2 grains) just as pressure is getting to 63,000 psi. RL-33 and N570 are right on the top of the list as far as velocity goes. RL-33 will add velocity with respect to most other powders as follows:
In your rifle you will likely want to back it down to about 101.8 grains to hit an accuracy node at a barrel time of 1.307 milliseconds.
With the 210 Berger it gets even better, looks like 102.5 grains of RL-33 with just get you to the accuracy node mentioned above at a pressure around 63,895 psi. Depending on the actual burn rate you get with your setup you may or may not be able to get there but if you can it should be sweet. Velocity advantages over the powders mentioned above are very close to the same except the advantage over Retumbo grows to 63 fps.
Of course all of this assumes a nominal burn rate and that is one thing you pretty much never get so you will want to work up to these levels to avoid any unpleasant surprises. Also, use Nosler and Berger data to start. Interestingly Berger shows velocities that appear very low and Noslerís appear pretty fast. I donít mention specific velocities as it all depends on your setup just like it did for them.
I'd watch your top charges a bit. 95 grains rl33 is top charge right now for my 300 rum with the 225 hornady and a 215 in rp brass. It seems rl33 is no different than some of the other powders in that it will take quite a bit different top charge on the heavies depending on their construction.