The pumpkin cannot be destroyed, cut down , wadded, saboted, or modified in any way.
Yes, but you can grow your own.
If I was in the comp, I'd make a clear plastic shell/mold for the pumpkin to grow inside. That way you could force them into a perfect sphere shape or give them golf-ball like dimples to reduce drag.
I'd also think about puting a space heater inside the gun's chamber.