any of the 90 grain to 100 grain bullets will do it. the bullet that shoots the best groups at that range is best. how far have you shot your .243 so far?? some that come to mind : 95 berger and balistic tip; 100 grain, horn sierra or nosler.
I had it out to 500 shooting jugs with the 70 nosler ballistic tip. I tried the 105 amax but they don't stabalize and don't 95 mergers call for the 1-9 also?