I am casting for my .375 H&H with the Lyman #375449 it is 264 gr. and looks a lot like what you have designed here, and is giving me good results , for me I do not want the bullet any lighter, but I am sizing .377 so I would make it to drop the bullet at least .379, you may get a few wanting it for the old 38-55 needing all of the .379 or more.