Other Zoraki/Alecto Problem

[Modski66]

I recently sold a Webley Alecto to a friend, but he has commented that after taking a shot it makes a 'pop' sound, and has had a few shots that he feels are low on power as the pellet had hit the target lower than his POA. I know he is an excellent pistol shooter, so have taken the pistol back to investigate. It definitely makes the pop sound, but I have tested the velocity at the three power levels and found very little variation shot to shot. Added some silicone oil to the piston wick and re-tested, but no change in performance.
As a side note, it is running higher than I would like after three pumps and suspect that either the blow-off valve is stuck shut, or a previous owner has fiddled with it.

Has anyone else experiences the popping sound, and if so, know what it is and if it is a problem?

 

[marflow 777]

it is a subject that has been brought up before, you can see from this post in August of 2012 that the subject was talked about
https://www.airgunbbs.com/showthread.php?615431-Webley-Alecto-POP

i got out one of mine out and there is a little spit-pop sound and with a MOD on it, it is a little more noticeable but at 2 pumps it works as it should

 

[Modski66]

Very helpful, thanks Mike!

 

[marflow 777]

the Zoraki HP-01 valve has had much written about it but understanding what does what and how gets complicated
to work on it you have to take half the pistol apart so and the make an adjustment and put it all back together and test and hope for the best and for me when testing is so hard it gets left alone if it works
the new HO-01-2 is even more complicated because they added trigger adjustments
do i think it makes the pistol a bad choice not at all but to understand how everything works without someone walking you through it to understand it 100% we do not have
how many people know the barrel adjustment to the Oring, should be made after 2 pumps, not many and when i first heard it i said what the hell
but was told that there is enough flex in the gun it makes a difference
now the short barrel guns are hard as hell to get to 3 pumps and the ultras will get to 4 pumps once because you will hurt yourself
now i must admit i own 5 of them and don't ask why and bit and pieces for all of them