I made a lego hand cannon when i was bored(you can reload like most of handcannons in destiny(if you want too see write in comment) and it shoots but not very well) :
Amazon.com: LEGO Pirates Cannon Battle (6239) : Toys & Games
Amazon.com: LEGO Pirates Cannon Battle (6239) : Toys & Games
Death Star Cannon 75246 | Star Wars™ | Buy online at the Official LEGO® Shop US
Automated Lego Shooter | Arduino Project Hub
LEGO MOC Compact Cannon with wheels by Xigphir | Rebrickable - Build with LEGO
Lego Cannon for sale | eBay
✓ LEGO How to make A CANNON! | WORKING - YouTube
LEGO Pirate Red Cannon Lot - Red Shooting Cannons (for minifigs) | Walmart Canada
LEGO MOC Laser Cannon by zaru_soba | Rebrickable - Build with LEGO