Carbon fiber is a bear to work with unless you’re casting woven sheets of the stuff in resin or epoxy like binders.
The first time you get carbon fiber stubble into your flesh from working on carbon fiber, you’ll swear off using the stuff ever again.
Extreme high pressure press compacting sintered metal around a rifled mandrel and simultaneously cooking in a kiln can create a low pressure barrel such for a .45. I am somewhat familiar with the process, can be done with simple 50 ton hydraulic press and a home made kiln. Durability? questionable but would make a Liberty style gun look prehistoric.
However, as several have pointed out, 3D printing with materials suitable for high-stress gun parts or precursors like wax models, is already feasible, and may make it into the small-shop/home-shop arena in the foreseeable future.