The UP3 is simpler, thinner, sturdier, and requires less parts than it's predecessor with no change to it's function or range.
This is my choice battle weapon.
Fires yellow rods 45 feet. Holds one elastic.
Step 1: Handle
2: Build this.
3: Build this.
4: Connect 2 and 3. (and add a gray rod as pictured)
5, 6: Connect 1 and 4. (and add two green connectors and a blue rod as pictured)
Step 2: Barrel
3, 4: Build this. (it's symmetrical)
5: Build this. (it's symmetrical)
6: Connect 3, 4 and 5.
7: Connect 1 and 6.
8-10: Build this. (it's symmetrical)
11: Connect 7 and 8-10.
Step 3: Assembly
Step 4: Firing Rod, Elastics, and Barrel Tips
2: Add duct tape and elastics as shown.
3: Add elastics as shown. Attach a blue, zero slot, connector to the firing rod in the noted location.
4: Attach barrel tips (acts like a funnel to make loading rods quicker and easier).