SpudFiles

The Mythbusters made an episode were they did a test to see if a sewer explosion could send flying manhole covers. The did a small scale test were they made a combustion chamber with a looking window, simulating a sewer. On a first try they put the methane and ignited it and it combuted. On the second try they put a bunch of springs and things that took space up on the chamber, on that try the explosion was faster and more violent.
I was thinking that the same principal could apply to potato cannons; putting some sort of metal peices on a potato cannon's combustion chamber could improove its power by making the combustion faster.

There is already another topic about this that was recently posted. Check the combustion cannon discussion.

That topic is in the Theories section. It's one of the first in the list below all the announcements and stickies. "Theoretical Combustion Cannon Power Improvement"