Sound Moderator

Despite what you see in the spy movies, what people call a "silencer" can't really be done in any size smaller than a beer bottle. Printed on normal 3D printers, this is a sound moderator: It won't eliminate the sound of an airgun firing, but will cut out the sharp "crack" that makes birds fly off and wives complain from the study.

It works by allowing the excess gas from the barrel to expand slowly in a series of chambers, shown in the cutaway image. If you use this with a firearm you will probably melt it.