Could I? Yes. Would it be cost effective? Absolutely not. The barrel it a solid 8 hour peice, another 20ish for the slide, and at $120/hr (standard shop rate at my shop), conservatively thats almost $3400 in just time. No way I would use supplied materials, so add material cost, special tooling cost, heat treat/annealing, coating, etc. This is not an offer to do it, this is just trying to bring some reality into light. Also you dont need to go to school to learn how to use a manual lathe and knee mill. Just watch some youtube and practice.