The move away from lead in military bullets has been going on for some time. In these cases the change from lead to steel cores gave longer bullets to maintain the weight. The designers, in almost all the cases I have seen, retained the same nose and boat tail shapes as the lead core bullets, just extending the cylindrical portion of the bullet, which in turn reduced the gyroscopic stability factors when used in the same guns as the lead cored bullets.
In tests I have seen problems with steel core and solid copper bullets, so pellets and their designers are not the only ones with problems replacing lead.