Re: 210"s in 300 Weatherby
I shoot a standard 300 wby /210 Bergers/Fed 215, in both my hunting gun and my match gun. Both are 30" Spencer 1-10 twist .330 neck. I Have found that RL 25 was the best. Most of the guys shooting 300 WBY sized cases in compitition shoot RL 25. I have run the gammit of powders, including Retumbo, AA8700, RL22, H1000, 7828, H5010, H870, ect..., and probably a couple others. I always came back ro the RL25. Very low ES. Retumbo came in a close second, with RL 22 third.. I shoot Molly in my hunting gun and took Retumbo up to 85 GR. I never hit the end, but 84 shot very well at around 3050 fps. I am at 80 G of RL 25. I had great accuracy at 83, and ran that for a while....backed down to 81 to save on brass, and again to 80 for the same reason. I am now at 2950 fps.
On my match gun I have only used RL 25 My match load is 74 @ 2780, and my hunting load is 83 G at 3150. I took it up to 85 G and had very very slight psi signs....but at 3290 fps. So, pressure signs or not....they were SMOKIN HOT. I think that if I wasn't using a BAT action, I would have definately seen some PSI signs!! Both are close in Accuracy, but an inch or two bigger group is huge in compition. I get 6 FPS ES with the 74 grain load, and brass will last FOREVER. I run +020 jam (+020 longer than just touching the lands) on both guns. If I use the magazine on my hunting gun I need to shorten things up a little to fit. Not much changes accuracy wise.
I can't find my records at the moment as far as where I was with H1000, but I know it didn't compare to RL25 or Retumbo. You would do fine with Retumbo if you were set on using it, But I would at least try RL 25. I am getting two new tubes chamberd up in 300 WBY, so I baught 25 pounds of it!!