octane89 wrote:What I will end up doing is using a interchangable barrel system and record my data. Since my cannon will be the constant, the barrel will change lengths (and keeping the same C:B ratio) to see the varying results. I can also "match" spuds by their weight and hopefully I will finish this soon. I will record as much as I can: muzzle energy, projectile acceleration (using GGDT perhaps), distance, etc...
Even if you can't exactly match the spuds weights you can measure the spuds weight and then correct the results to a constant weight.
If you have the spud's weights you can also calculate the kinetic energy of the shot. This is probably a much better measure of the gun's performance than just the muzzle velocity.