Not the 270, no, but I did write Sierra on using their 250 gr. 375 in mine. They gave me some load data, and told me that it would be a fairly good load, although at the velocity, (like 1600 fps if memory serves), expansion would be nonexistant.
I'm thinking that the light 375 rounds are designed around the 375 WIN, and the heavier ones for the H & H. I also got a note from Hornady once that told me the 220 grain flat point should only be loaded to reduced velocities in the H & H case. Stands to reason, I reckon.
I 'm looking real seriously in using a hard cast with a wide meplat, and a 210 barnes X in my 375 WIN, whenever i can get around to it.
Good shooting.
Steve