The larger air cannons, one of which exploded at the event this year, can hurl pumpkins over 4000 feet (1200 meters). Even the gentler centrifugal and catapult devices can attain distances of 2000 feet (600 meters) or more. Fortunately, the safety precautions taken by the crews prevented the barrel explosion from injuring anyone, and shattered remnants of the device's PVC (polyvinyl chloride) plastic barrel became autographed souvenirs for attendees.
The full AP article is linked from the "original article" link below. The Punkin Chunkin event home page is http://www.punkinchunkin.com/.
Contributed by Lord Zachariah von Marksburgh