Just completed this design for a friend. I haven't seen any 1.5 unit printable cannons before, so I took my LPC design and added two more rings of ammo. Actual tested magazine capacity is 80 rounds, so you have a few rounds to tweak with before battle. File includes both left and right versions, each with a small (1.5mm dia) or large (2.5mm dia) gas bypass for pressurizing the magazine. Small is intended for MAV-2's or other low-flow valves, while Large is for high-flow valves such as BC Combat Gear solenoids. I recommend printing around 30-40% infill, at 0.1 to 0.15mm layer height. 3 layers for a .4mm or smaller nozzle, or 2 layers for a .5mm nozzle. Make sure you pour acetone through the internals (ammo ramp, gas bypass, and riser/elbow section), and/or do an acetone vapor bath to harden the structure. As with any 3d-printed cannon, your results may vary.