I've done a lot of load development with my 300 RUM over the last couple of months. The 200g TTSX (now called the LRX) has been the best bullet that I've tried out of my Sendero SF II. My current 'best' load is as follows:
Powder: Ramshot Magnum, 96.5g
Bullet: 200g Barnes LRX
Primer: Remington 9 1/2M
This load is shooting 3207 FPS with 3/4 MOA accuracy. I've shot it out to 760 yds with great success. The BC on the 200g LRX is higher than Barnes claims, based on my testing. When I try and match the ballistics of my load by trying different BCs in JBM I'm getting close to the BCs of Bergers 210g Hunting VLD. I need to fiddle some more to confirm this, but it looks promising right now. At a minimum, it's definitely higher than the BC stated by Barnes.
Here's a link to a thread where I've posted the results of a bunch of 300 RUM load development:
load workup for 300 RUM...