spudfarm wrote:you are right dead space = bad
That's an over generalisation.
Too much dead space is bad, however, in small amounts it can actually improve a launcher's efficiency and power, by providing a store of air that can provide higher flow than the main valve.
The optimum is quite dependent on the round, pressure and the dimensions of the cannon, but usually the results of optimising this are only a couple of percent added to the muzzle energy.
But a little is better than none, so people shouldn't fret over a cubic inch or two.
However, on this scale, it's going to do more harm than good.