From my research you can go as heavy as 69 grains but at that weight powder levels will need adjusting to insure stability and accuracy. Stay with 65 grain and lighter you should be just fine.
Mine is also 1 in 9 twist and, after a LOT of shooting and testing, I can say for sure that 62 grain works the very best, at least in my rifle it does.
Especially like the Remington 62 grain Core-Lockt.