Steve
I prefer to focus towards Miller on the heavier density bullets from the .338 and up, for example the 400 grain 375 cal used had a SF of 2.16 , thats a spin rate of 302490 rpm out of my 375 Warner. I have relied on the Cold Bore program from Patagonia in which will utilize either Millers or Greenhills formulas.
When looking at density within a bullet it is very sensitive to mass weight, mass weight still trumps. I have always believed there is a balance between mass weight and speed, the BC only contributes to that. Folks are all jacked up about shooting the Highest BC bullet but for the most of them they don't understand trueing BC and still having enough horse power or gas to even think about pushing a heavier " higher BC" bullet. If you don't have the gas you don't gain anything.
A while back I ended up testing some leadcores on the 375 versus the solids it was designed for, you were out of stock so I ended up buying some from our folks in Canada. They had a tuff jacket but when testing a 16 to 7.7 gain twist which is somewhat easy on the bullet they in turn could not make it to the 100 yard target before blowing apart. I know your lead core bullets are known for having a strong core it would of been a good test. But to all reading remember a twist as tight as 7.7 is meant for solids.
HAPERC
When thinking about running solids in the lighter class bullets as your example the .264s I would be using a 25 cal conversion. Remember nothing is set in stone they are only guidelines and estimations based on testing.
A comment from above
Some who assumed or heard from someone who probably assumed as possibly stated above - seriously a solid needs to spin slower then a lead core or it tumbles - No solids need to be spun faster then the common lead cores, also the 375 Chey Tac has been preforming extremely well in the shooting world and is very comparable in cost to shooting a 338 LM and what? Anyone shooting this round is so strapped they can't afford the other necessary items to complete their build and shoot well. Its BS like this that ticks me off because the folks that are trying to learn don't know whats valid and whats not, how asinine this comment is from above.
Osoh
JH