Well after over a year of procrastinating, I finally took the plunge and purchased a new cylinder and piston

Imagine my embarrassment when I went to fit it - after removing the hand guards I was about to unscrew the gas cylinder when I noticed that the gas cylinder retaining pin was missing entirely

nzl1a1collector - you were right

Now I wish I'd checked first before buying the parts

On the positive side, I now have a spare piston and gas tube - and I do intend to do a lot of shooting with this rifle