https://www.instructables.com/Knex-Blow-Back-Full-Auto-Rifle/
K'nex Blow-Back Full-Auto Rifle - Instructables
K'nex Blow-Back Full-Auto Rifle: It's finally done, and here it is. This is a blow-back, fully-automatic, controllable, (the shots don't just burst out), K'nex...
full auto riflek nexblow backinstructables