I have been printing for about 4 years and have used about 15-20 spools of PLA filament. My prints are my 3D designs for new sights. The times to print run from 2 -30 hours and then the finishing work of installing the electronics is done to complete. For prototype work, the 3D printer is extremely efficient tool. I can design and draw, using Fusion 360 program, then converting using Cura program and print, using Ender printer. I then assemble, test shoot and repeat all within 3 days of having an idea. No other process is near that level of efficiency. The PLA filament is not premium material, but I end up throwing 3/4 of all my prints away after testing. Since there a few standards for gun, air gun and bow manufacturing, most of the designs are specific to each model. I have printed and thrown away many hundreds of mounts and it would have cost me a fortune if I would have had them all machined. The amount of time to machine my mounts would have limited what I would have gotten accomplished. My prototypes are meant to prove out a concept. They are not ready for the average shooter. They are not meant to hold up to the extreme work-duty that some think is necessary to be a quality product. Shooters of target rifles would not test the reliability of their equipment by beating on it with a half-filled water bottle. There have been a lot of good comments about 3D printing, and I look forward to reading more.