Neither am I, but I can tell you based on my background/experience with machining and molding, including thermoplastics, that unless you have the ability to injection mold this stock (and I do mean injection mold, not pour molten polymer into a female cavity), the result is likely to be very weak and ugly as sin.
A milled piece would have the strength, but still be fugly and take at least as long as hand carving wood. Trust me; I have milled buttstocks from ABS and Acetyl stock.
Conversely, if you spend as much time shaping and sanding a piece of wood as you will trying to get this design done right in CAD/CAM for a 3D print, you'll have a very functional and much more aesthetically pleasing finished product.
The problem I see is that you are looking at material strengths based on data sheets, but not really accounting for how the manufacturing process affects that. Just as there is a substantial difference in strength with alloys based on whether they are cast, sintered PM, MIM, extruded, forged, etc, so is there a big difference with polymers. Heated filament printed pieces are about the equivalent of lead soldering steel wire to form a 3D shape.
3D printing has it's place, but this ain't it. It's great for prototyping a design before going production with conventional molding or machining processes, but even using higher strength materials, the manufacturing process results in strength that is far inferior to injection molded or machined pieces. Cody Wilson was using a $60K printer with high strength nylon filament to make his printed lowers, and still had to reinforce the heck out of it to withstand the same forces that injection molded lowers have handled with far less bolstering.
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