That is a very interesting post. I have made jacketed bullets for the .44 Mag. I use the .40 S&W brass to swage over cast lead bullets. My problem has been accuracy. I think years ago the accuracy expectations were not as great as they are now. The science of making our own bullets is a very interesting pursuit. Nice post.
Bullet cores have to be made from pre-molded cores or cast bullets. It is impossible to cast cores into jackets and eliminate air pockets. That is where your bullet weights will be off. Modern bullets have "Ballast" points this creates better accuracy. I can not seem to match this with my home made bullets.