Any machinist in your area should be able to be contracted to do it. But if you not using lead or copper or any other material of that malloiblity, you sure wouldn't be able to shoot it in anything with rifling. It would build pressure so quick, and would give any.

Are you saying armor piercing? like to cut off the head of a bullet and transplant it? Its none of my business, I believe the ATF would have issues with that, kinda like dum dums or liquid tephlon coated bullets. I would tread a tad lightly on contacting reputable bullet makers wanting such.