A pair of 1/48th scale 40mm grenade launcher for the Airfix modern british infantry kit.
Cut the front end off the SA80 and replace with 1 of these parts. They fit best on figures 5(kit part 37) and 6(kit part 46) in the Airfix kit instructions.
I've printed this in White Acrylic Plastic as a test of the material. I would recommend using the Frosted Ultra Detail would produce a more detailed result.