I tested it out with red-rod sized slingshot ammunition and two tied 64-sized bands, and I got around 50 or 60 feet. It's not as good as the old one, and I need to make the barrel longer to get more range. The trigger is hard to pull, but it becomes easier with practice.
I will be posting this once I have the range satisfactory (around 90 or 100 would be awesome) and the barrel lengthy enough.
UPDATE: I have improved the gun. The stock is finished (it was lacking some minor details), the trigger is more reliable (now with guard, too!), the back handle connection has been removed, and the handle is now much more comfortable. The entire gun is also carry-strap compatible, as shown. The range is also better due to the longer barrel.