G'day John, long time no hear.
I started this same thing ìn 2016 but got side tracked. I do mean to finish it, one day. With your skills yours will be great I'm sure. Here's a couple pics of where I got to. To get the sharp breech area edges I had to screw the rear of the gun onto the body as you can see. All the best. Ray
I initially 3d printed it then machined them.