Silly question - how many watermelons?
There would literally have been thousands - if not tens of thousands - of melons in that "barn", or whatever it was. They had around 20 people picking melons for almost a week. If you're picking a melon a minute, that's 60 melons an hour. 10 hours a day, that's 600 melons per person. 20 people picking, that's 12,000 melons.
Even if it's half that, or a quarter of that, it's not as if they brought thousands of bullets with them. They could only have shot up a couple hundred melons - at the absolute most. Right?
I want the doctor to take your picture so I can look at you from inside as well.