S510 Classic with bad grouping

[patratel]

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 thing and the barrel; so then I glued it with a bit of Loctite 638 onto the barrel, into it's place. The O-rings are still taking the vibrations from the barrel onto the shroud, as they are supposed to do. I noticed no noticeable difference in grouping before and after gluing -- and believe me, I did shoot a good few hundred of shots before and after, with different conditions and all in a bunker (no wind whatsoever).

[patratel]

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 of the cheaper models. A possible problem comes from the design of the turrets and reticle adjustment. I think the reticle may be supported by a single diagonal spring. If the spring is broken or damaged the reticle may be moving both horizontally and vertically.

I try to mount scopes so the reticle is close to optical centre and near the middle of the adjustment range, using adjustable mounts or shims if necessary. (If the mechanical and optical centres are not close to each other the scope must be faulty). Is the reticle set close to the mechanical centre of the adjustment range? If it is near the end of the range, where the spring is under little/no pressure, the reticle can "float".

Indeed, sometimes I see 2 peaks but only here and there (perhaps one in 20-30 groups that I shot?) -- is it only statistics and lack of enough shots, or is there something going on...

I don't think it is a parallax error, I corrected for that. The scope is a 8x-32x 50mm Hawke which I bought new, was about 500Euro about four years ago. Does this fall in your 'cheap' category? It never had any extreme shocks (except from shooting, of course). I normally have it on 24x for 50m and it works fine. I do see some aberrations such as comma coming in at extreme magnifications (8x or 32x) but other than that, I never rally noticed any sudden change in shooting accuracy, from the beginning -- that is four years back.

Now I have another scope from a friend, it is another Hawke (6.5x-20x and 40mm I believe, but better quality or at least better finished than mine). I don't see any improvement when shooting with his, but I need to retest later this week to confirm..

I think if the reticle spring would be damaged, then the problems would be much larger than what we see now, wouldn't they? I also put some thin metal sheet onto the back mount, to raise the scope a bit from the back so that the optical range is somewhere in the middle of the mechanical range -- otherwise I would have been near the end of the mechanical range, indeed. I will check that once more. Normally, I don't really touch those knobs once they are set onto 50m distance.

[patratel]

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 .

take care Michael and fingers crossed we'll get to the bottom of your problem .

has it been suggested that you try shooting it without the shroud or anything on the barrel , what ftlbs is it doing ? have you tried lighter pellets or weighed and graded pellets ?

rgds.

julian.

Thanks, just take your time! I did try lighter pellets, from 14gr on until 18 and higher -- have a look in that document. While reading, don't bother the formulas, it's just about the results, grouping, and histograms mostly.

Unfortunately, I cannot shoot without the shroud due to noise limitations (there are quite a few houses nearby and we have a strict set of rules to follow). I might try to go visit that bunker once, but that's not for now I think...

I did try weighted and inspected pellets -- most of my tests were done with carefully weighted pellets, thousands of them altogether.

[patratel]

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 detailed investigation. You are welcome!

PS ..I have an S400 and a couple of S200s that group like something crazy. We can use them as a reference..

Well, thank you for the invitation! I'd love to come and visit you and compare the accuracy and stuff.. The first time I will visit England I will let you know! I am from Belgium... So I am kind of 'over the horizon' at this moment, unfortunately..

Properly speaking, I am quite confined around my living place and I can't even get by air bottle filled because of covid (excuses). I'm at 120bar now on my air bottle, so whichever last tests I'm gonna do, they will be my last until I can reload again...

Thanks,
Pat

[patratel]

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' rings or if worn/rubbed it should be replaced and new 'O' rings fitted. Its a push out part towards the breech end of the shroud. The washer you fitted should be removed. The barrel should not move around inside the shroud.

Remove the moderator and tap the threaded end onto white paper and see if any lead fillings come out. Also, carefully check just inside the pellet exit end of the moderator for grey lead marks. Both these would indicate pellet clipping.

Here is a link to a post on how I resolved clipping.

viewtopic.php?f=15&t=5706#p40675

In an attempt to decide if the barrel has a problem, fill the rifle to 160bar, remove the moderator and clamp the rifle firmly and shoot 10 pellets at a 30mtr target(you may have to move the target around to line it up) and check the grouping. If good it's almost certainly moderator clipping so follow the link. A loose barrel inside the shroud can also cause poor grouping.

If you still have problems after the 30mtr target test remove the shroud and check the barrel isn't loose within the breech. If not try the 30mtr test without the shroud and with the barrel supported.

Julian can supply any parts you require.

To check if the loading the pellets is damaging them don't use the magazine and manually load them into the breech and test again at 30mtrs.

If I think of anything else I will post my thoughts.

Regards

Very useful remarks, I need to comment shortly.

I did not add any washer, I just glued the Al spacer onto the barrel with Loctite and that's all. The O-rings are still there. Gluing did not change anything.

I sometimes shoot with and sometimes without a moderator. In either case, the grouping is not what it should be.

I will follow your clamping advice, once I can refill my bottle. I cannot remove the shroud due to sound limitations on the shooting range.

I do a manual load for this kind of tests, by the way.

[patratel]

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..