Frame: Generally 3D-printed flat on its side using ABS or PLA plastic to maximize layer strength and prevent the frame from splitting under internal pressure.
Printed vertically using a highly durable nylon material (such as Taulman alloy 910). The 8-shot variants often incorporate thin-wall steel tubing inserts inside the chambers to add structural reinforcement.
Originally engineered in 2015 by mechanical engineering student James Patrick, the design has been modernised and updated into various configurations, including the Mavric Washbear PM 522 double-shot and six-shot high-detail models.
