Air Arms Owners Club

I had fitted a reg into my S510, but always had a slow leak from the breather hole. Changed all the o rings and polished the cylinder. Then I watched Robert Lane videos and he said 99.99 % of breather hole leaks are from cracks in tanks, so I had a closer look. Well, I'm not surprised its leaking with all those channels running through it. That's the breather hole there too.
Anyway, as advised I took to it with some Emery cloth, and that fixed it thank goodness.

Guessing AA don’t design their cylinders for Lane regs, rather the other way round. So its bad luck on you rather than poor quality by AA .

There have been cylinders in this forum with a noticeable groove along their length that are too deep to be polished out.

Having said that, if that was mine I would have replaced it - they look too much like stress cracks.
Tin hats on!

Of course, I'm sure if AA were putting regs in, the cylinder would be better. If those marks are just part of the manufacturing process, it's good to know before hand, as I feel I'm fortunate to get a seal. Just something to go into the memory banks for next time.
I would expect stress cracks to be on the outside? Unusual marks anyway.