Re: 338 Sin
I think you are to slow for a 200 grain bullet in that size case. I think you will be better with a rate range from 4350 to re-22. Magpro, 7828 might fit and I have something that would make the 200 shine which is WMR. H-1000 and re25 are to slow with the 200 grainers. Get with me on a pm. I would like to help you with it. I have quite a bit of experience guessing starting loads for new wildcats. I am confident I can get you over 3200 fps with the 200 grainers. My 338 RUM loads with the 200 grainers hit in the 3300's.
Predictions are difficult, especially when they involve the future