Here’s a set of 3D printable files for a simple 40mm grenade launcher. This launcher is compatible with most moscart shells, including taginn shells.
In addition to the printed parts, you will need some 1/8″ steel rod to use as pins for the trigger mechanism and the long shell holder. You will also need a compression spring to return the trigger to its rest position. The grip will also need to be glued or welded onto the main body piece.
This launcher can use one of two methods of holding the 40mm shell in place. Either the long cap piece can be used to push and hold the shell in place, or the yellow shell grip piece can be used to grip the rim of the shell.
Don’t have a 3D printer? A set of prints and hardware are available here.