Additional Materials: - 50mm Outer diameter 44-46mm Inner diameter pipe (polycarbonate or PVC): 480mm length - 10mm acetal/delrin/nylon rod: 210mm length - K25 Primary spring from Mcmaster or other large spring (1x) - 44mm OD O-ring (1x) - 16mm ID O-ring (1x) - 16mm elbows (2x) - small compression/extension springs (buy an assorted box) - 16mmx2mm aluminium bar (2x 202mm lengths) - 15mm copper pipe (150mm and 55mm lengths) - 16mm PVC pipe (260mm length and 2x small stubbs) - 20mm clear PVC pipe (~70mm length) - M3/M4 Cap head and countersunk bolts of various lengths - 5mm threaded rod (could use a cut down M5 bolt) Overall cost of other materials is around £10 - £18 per blaster depending on part sources. Make sure to print the Muzzle piece in a bright colour so that it doesn't look like a replica firearm. Slots need to be cut in the 50mm pipe for the priming mechanism to work. I used a jigsaw, but you could drill a series of 7mm holes and file it out into a slot.