Updated firing pin to have twin bars to allow for rubber band to stretch around the muzzle for added power. (Print this part 100% infill).
Added grooves to the muzzle to keep rubber bands in place.
Can still hold an internal spring
Print Settings
Printer brand: Creality
Printer: CR-10
Rafts: No
Supports: No
Resolution: 200
Infill: 20
Filament brand: SUNLU
Filament color: Orange
Filament material: PLA
Credits:
NeilSM