I reckon if you can knock out machine, cast or 3d print receivers which now you can do in a metal material to the correct identical spec pattern etc you could be onto a winner in the spares part world. Must be pretty devastating finding your prized Innova forming a crack on the body, bit like opening a gun case on your favourite airgun only to find it covered in rust, a good topic what members here would consider a air gun disaster, ie stock snapped in half etc.