No doubt it varies from state to state.
Best check with whoever actually knows your local and state laws to be sure.
Considering all the folks making and shipping bullets, it’s not too likely there are restrictions to making just the bullets, but you never know.
To the best of my knowledge, no, it is not illegal to cast or swag bullets. I’ve done tens of thousands of my own. The only legal issue would be if you fully loaded the round and wanted to ship them. You can NOT I repeat, NOT ship ammunition through USPS. It must be another shipping method like UPS, or FedEx.
Thank you all for your answers. I think that really sort of answers my question. I guess any state law could be unusual, but it seems the answer that is that in general yes you can make just a projectiles or disassembled cartridges in kits and then it’s not so regulated. OK. I just made a 45 ACP THV (Tre Haute Vitesse) lineup for shapeways based on the website I read on that particular type of cartridge. Assuming they’ll print them, they should be pretty cheap. And they would be available in brass, and other materials. Silver bullets too.