I can not help from my experience - I never loaded any. Just looked in the Lyman Cast Bullet Handbook - page 172 - they only show up to 200 grain in 303 British - for what it is worth, they show SR-4759 as their preferred powder, although they also list Min and Max for 5 other powders. Same information shown in Lyman 50th Reloading Handbook - page 277 - same powders - was for bullets cast from Lyman #314299 mould. Not at all what you asked for, but maybe a beginning??