Rifled Barrel for #MFUKLC

Continuing my build for the Mega Fun UK Laser Challenge I built a barrel for our ping pong ball gun. The barrel is made from dozens of stacked slices, I used a section of 41mm waste pipe to help keep them all aligned (I cut a slot down the side to make it fit neatly into the barrel). As I was stacking them I realised that If I twisted them round I'd get a fancy styling on it. Yes I realise rifling should be on the inside but in this case it wouldn't work anyway so this is just to look good.