Recently I decided to make a potato gun/launcher. This here page is the 2nd cannon I made. The first cannon was simply thrown together without any specific dimensions (however, it works great). After some research I found most of the information reported that a 1.5:1 Chamber to Barrel ratio was best. So with some help I created 2 calculators to help with creating a potato gun/launcher. Because PVC comes in specific sizes, the first calculator helps find a good Barrel Length based on your Chamber Diameter, Chamber Length and Barrel Diameter.

The second calculator finds a good Chamber Length based on your Chamber Diameter, Barrel Diameter and Barrel Length. Remember to measure the Inside and account for bushings, plugs, caps and even the amount of pipe slipping into the fitting.

My present potato cannon is designed for tennis balls. It has a 4" Chamber that is essentially 8 1/3" internal length. The Barrel nets out to 20" the actual cut length is 22" because 2" slips into the bushing. The Chamber consists of 1 - 4" Female socket adapter and threaded plug, 2 - 4" Couplings one of which was able to slide right over the 4" pipe increasing the burst strength and finally a 4" X 2.5" insert bushing.





Enter Chamber Diameter Value, Chamber Length Value and Barrel Diameter Value.
This calculator will display the Recommended Barrel Length based on 1.5:1 Ratio.
All Values In Inches/Decimal.




Enter Chamber Diameter Value, Barrel Length Value and Barrel Diameter Value.
This calculator will display the Recommended Chamber Length based on 1.5:1 Ratio.
All Values In Inches/Decimal.





So here is my 4" X 8.3333 Chamber with 2.5" X 20" Barreled Cannon.







I purchased 2 Weber 7510 igniters giving me an extra button and the 2 ignition source pins seen here below. I also drill a small hole in the barrel end about 1" up to put in a pin to stop the projectile from entering the chamber.







Fuels I have tested Old Spice High Endurance has Butane, Starting Fluid works real good it does require just a very small spray, of course Aqua Net non scented works good a little messy, and a new comer Cavalier shoe water proofing silicone works good too.