Yes - the longer monometal bullets will require faster powders taking up less space. There should, however be no problem in achieving "book" speeds.
In 1912, the ballistics were: 2,600fps for 270gr. and 2,400fps for 300's. Those are the ballistics, with which the .375 earned it's African all-round game killing reputation.
-------------------- Daryl
"a gun without hammers is like a Spaniel without ears" King George V