[vindicareassassin]

Its widely accepted the optimum ratio of cylinder to barrel volume is no less than 1.7/1 for around .3 bb's and for around the .4 mark a ratio of 2/1 is good.

 

[vindicareassassin]

From what I've read on ASM there comes a point when barrel length does not matter anymore and that number was either 400mm or 455mm.

Anywhere between the 2 is good, especialy for a normal length cylindered AEG shooting upto and including .3s, you can get away with a 509mm barrel in full cylindered bolt actions and long cylindered AEGs as there is enough volume of air to support it.