It turns out it was the barrel itself: choke too narrow. A different barrel with better choke does not show this problem.

So yes, a newly bought AirArms S510 (mine) can be bad from the beginning, despite the expectations..

Hi Patratel, I've read through the various posts about your problem. Early in your postings you said you glued a washer onto the barrel because it was moving around within the shroud and it was still moving, if I read it correctly. You also had Al fillings showing. The Al spacer needs 2 new 'O' rin...

Hello Pat ... (Hope you dont mind me shortening your monicker) Where are you in the country? If anywhere within striking distance of Rugby, Warwicks. come round to our house and we can do a side by side test with some of my rifles and draw up a rectification plan. I have the time to spare for a det...

just to let you know i received your 191 page pdf Michael , it might take me a few days (make that years of studying some of those formula's you've used , they are way above my pay grade / academic grade :-) :-) ) to get through it :D :D :D :D . take care Michael and fingers crossed we'll get to th...

You said that the distribution is flat or sometimes 2 peaks. I think this indicates something is moving. I agree with Rog, it could be caused by pressure on the barrel. I'm assuming it is not simply a parallax error with the scope. I don't know what model of Hawke scope you have but I'm not a fan o...

but starting to look like the shroud putting pressure on the barrel via the barrel tube support ( the little silver thing with the O-rings S600-3 ) About that 'little silver thing with O-rings' , I had a look at it a while ago (also then grouping was bad) and saw there was wear between this silver ...

Which A/A moderator/silencer is it, aQ-tec possibly ? but starting to look like the shroud putting pressure on the barrel via the barrel tube support ( the little silver thing with the O-rings S600-3 ) I'd remove the shroud complete with silencer, And see what happens . Rog I believe the moderator ...

some update on these possible failure modes - changes in POA vs barrel alignment, i.e. something loose either in the scope, action or stock --> changed scope and tested last week thanks to a colleague, no noticeable changes in grouping noted; will compare again this week, if wind stays down. - barr...

Just out of interest, have you tried shooting it without the shroud fitted? I've never liked shrouds on the S510, would have preferred a full length barrel, And never really understood why they didn't do it, they did it on the ultimate sporter, So why not the S510 😡 I haven't tried this one, yet. A...

For the regulator remarks, I've already posted some more info. For lending another scope, I'd have to ask some of the other shooters; typically people don't really borrow things to other in our club, is my perception. And the store where I once bought my rifle was taken over by another one, which is...