PVC Air Cannon Cold Drop Testing

Since building two PVC air cannons, and having a background in fracture toughness of PVC pipes for backyard roller coasters, I decided to see if a pressurized air cannon dropped on a cold day would be dangerous, as in explode.
Temperature 27 degrees F (-2.8C)
Drop height 48 inches (1.22 meters)
Air cannon pressure chamber: 4 inch diameter (102mm) schedule 40 PVC pipe, 10 inches unsupported length
Measured PVC thickness 0.255 inches (6.477 mm)
Approximate weight = 12 pounds (5.44kg)
Virtually no sunlight UV exposure (known to embrittle PVC), as the cannon was painted right aver fabrication.
Pressure in chamber during drops = 80psi (552 kPa)
In the first test, the air cannon was dropped on a triangular ceramic tile, with no damage.
In the second test, the air cannon was dropped on a rock. The cannon broke at the threads of the 1-inch PVC fitting. Threaded connections, and the large change in mass, result in a double stress concentration at this connection. So the pressure chamber survived two drops on hard pointy objects. But the threaded connection failed, which was unexpected leading to the conclusion that threaded PVC should probably be avoided in making air cannons.

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Hmmmm…. Are we planning on sending potatoes into low earth orbit?? Count me in!