So, the next time you see a LEGO bin at a garage sale, don't look for the instruction manuals. Look for the loose Technic pins, the worn axles, and the dried-out rubber bands. Someone else's trash is your ammunition. Now go build something that snaps back.
The most common mechanism is the "Auto-Fire" or "Gatling" mechanism, which relies on a simple truth: a rubber band wants to return to a state of rest. Builders create a flywheel or a rotating cylinder (using Technic gears and turntables) where rubber bands are stretched between a fixed "catch" and a rotating "firing pin." As the crank turns, the pin releases the band exactly when it aligns with the barrel. lego rubber band guns
A standard LEGO rubber band gun firing a single #33 band (1 inch long) at a target 10 feet away feels like a firm flick on the nose. A quad-barrel, torsion-loaded sniper rifle firing a heavy #117B band (4 inches, high tension) will leave a red welt for an hour. It will shatter a wine glass. It will knock a LEGO minifigure off a shelf from across the room. So, the next time you see a LEGO