Sniper+assassin+hack

These provide the tension for the firing mechanism. Scissors: To cut specific parts like the trigger and scope. Assembly Steps

Fold thicker sections of paper into rectangular or "L" shapes to create the grip and shoulder rest. Glue these to the back of the barrel. The "Hack" (Firing Mechanism): Cut a small slot in the top of the barrel. Sniper+assassin+hack

If you're a fan of games like Sniper 3D Assassin , you can model your paper gun after specific in-game rifles like the Kar98k or AWM by adding a "bolt-action" paper handle. These provide the tension for the firing mechanism

Stretch a from the front of the barrel back to the trigger mechanism. When you pull the trigger, it releases the rubber band (or a paper pellet pushed by the band). Glue these to the back of the barrel

Roll multiple sheets of paper tightly into long tubes. Slide one tube inside another for extra length and reinforcement.

Use black or camouflage construction paper for a more tactical appearance.

Create a "trigger" using a small paper lever or a folded hook.