Based on a design by Matsuo. The M41A Pulse Rifle from the movie Aliens canonically chambers 10x24 caseless armor-piercing ammunition. This print simulates the Nitramine 50 that forms the body, drilled out for a 10mm FMC pistol bullet (.40 SW) and counterballast weight (I used cut-off bits of 40/60 solder).
Printed at home on an M3D Micro, and I actually recommend downloading and printing on a consumer printer, as the print lines and other artifacts are a desirable design element.