Wouldn't it be easier to adjust the scope instead of pursuing the elusive extra 300 f/s?
Assuming, of course, that the scope is accurately calibrated for the higher velocity, in the first place.
Might be a silly question, but have you checked the point of impact against the scope settings, at the distances you need?
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”