S510 Classic with bad grouping

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patratel
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Re: S510 Classic with bad grouping

Tue Jul 07, 2020 5:11 am

poguemahone wrote:
Fri Jul 03, 2020 9:45 pm
if the 510 has 2 little pads inbetween the cylinder and stock at the front, same as the 4*0 series, then float the cylinder ;)
most guns are fine with the 2 pads, the few that arent wont shoot accurately unless you float the cylinder. mine was one of those guns :lol: takes less than 5 mins to do .
I donnow about those pads, I will need to look -- put it on my TODO list. Anyway, I will check it. I will have to remove cylinder pressure for that, I guess. Perhaps anyone else knows about the (non-)existence of these pads on S510?

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patratel
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Re: S510 Classic with bad grouping

Tue Jul 07, 2020 5:23 am

tonyc wrote:
Fri Jul 03, 2020 8:47 am
... I would just try loosening and carefully re-tightening the barrel band just to allow the barrel to centralise. Check the barrel crown and breech for any burrs, though I'm not aware LW barrels suffer in this respect. The other possibility is the magazine or loading is damaging the pellets. If you have the old-style magazine advance spring it could be slightly bent which can alignment for loading.

It's interesting you say there are possibly two peaks in the distribution. That could indicate something is moving in the barrel to line-of-sight alignment or possibly the stock or your technique. You haven't said in which direction the two peaks or flat distribution occurs, if this is constant direction or entirely random. It's also not clear if you are seeing 40mm groups from 10 shots or this is what you get if you shoot 25+ consecutive shots.

A concern at the moment is your adjustments to the reg pressure, If you haven't done so, I suggest you chrono a full string. Adjusting reg pressure between 130 and 160 bar I'd expect to see a change in the cylinder-pressure dependency. +/-2m/sec is not brilliant for a 10-shot string but if you also have a drift in moving average as the cylinder pressure reduces you may be seeing much larger variations over 25+ shots. +/-3m/sec could be giving a (near) vertical spread of 10+mm. If you also set the reg high, say 160bar, and run a few strings, each including at least 10shots on reg and 10 shots off reg. Look for shot-to-shot variation on and off reg. This may give an indication of erratic performance of the regulator (on-reg variation) or action (on and off-reg variation) . I'm getting typically no more than +/-2fps in a 10-shot string and <10fps spread over the full regulated profile - that's with sub-12ft lb .177 with Altaros reg, not the AA reg. Changing reg pressure by 20bar would easily push the spread to over 20fps.

If you know your regulator and action are consistent you can look at other mechanical causes. Have you changed your scope to eliminate that as a possible cause?

That's about all I can think of at present - hope it helps!
in short
--> The loosening and re-tightening the barrel has happened a few times already, no change
--> check barrel crown and burrs for burrs: will do that
--> magazine/loading might damage the pellets: I also tried manual loading (with a tweezer) and loading with a self-made 3Dprinter piece; no improvements seen
--> adjustment of the reg pressure (my S510 does NOT have an internal regulator but one on the air bottle): chrono and grouping correlation was done plainly and per each pellet type, even various batches; also done with a more expensive regulator (again, on the air bottle and not inside the AA, the AA gas cylinder is original and without internal regulator). with good pellets, the digit doesn't change (<1m/s as it was set for metric units).
--> scope: I haven't changed it, as I would need to borrow one and people are not so generous to borrow me one of their scopes... in some way understandable, in other not really, but ok.

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patratel
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Re: S510 Classic with bad grouping

Tue Jul 07, 2020 5:31 am

In the meanwhile, it seems AA is willing to have a look at the state of the barrel. Any of you know what they would be looking at? is this the next step I should take once I exclude the remaining possibilities (flushing cilinder and scope)? Or is there anything else?

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Roger5
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Re: S510 Classic with bad grouping

Tue Jul 07, 2020 12:15 pm

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 😡

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tonyc
Posts: 376
Joined: Mon May 29, 2017 10:55 am

Re: S510 Classic with bad grouping

Wed Jul 08, 2020 10:23 am

patratel wrote:
Tue Jul 07, 2020 5:23 am
--> adjustment of the reg pressure (my S510 does NOT have an internal regulator but one on the air bottle): chrono and grouping correlation was done plainly and per each pellet type, even various batches; also done with a more expensive regulator (again, on the air bottle and not inside the AA, the AA gas cylinder is original and without internal regulator).
I'm confused now. You mentioned "regulated air pressure" in your original post but the gun isn't actually regulated? So you are just referring to the cylinder pressure you have filled to for your tests? Whatever, we've established you have no velocity variation and the pellets aren't getting damaged in the magazine, so we must be looking at one of the following:
- changes in POA vs barrel alignment, i.e. something loose either in the scope, action or stock
- barrel either damaging pellets or not directing them consistently
- pellets deflected by shroud/moderator.

If you've checked the action and stock as far as you can, that leaves the scope, barrel or, as Rog says, the shroud.
I'd check with a different scope before involving AA, just to avoid embarrassment that it's not the rifle. I'd also try without shroud end cap and moderator.

Surely you can find someone who'll lend you a scope. The shop perhaps? It doesn't need to be new or anything expensive. Where are you located?

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Roger5
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Re: S510 Classic with bad grouping

Wed Jul 08, 2020 10:59 am

I believe patratel is talking about tethered benchrest, in which case the reg is attached to the dive bottle and not in rifle.
It might be handy to know where he's based ?

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tonyc
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Re: S510 Classic with bad grouping

Wed Jul 08, 2020 1:56 pm

Roger5 wrote:
Wed Jul 08, 2020 10:59 am
I believe patratel is talking about tethered benchrest...
Ah!... didn't think of that... but reg misbehaviour is ruled out I think.
Ref your comment on barrel and shroud unlike the Ultimate Sporter, I've always wondered why from the other direction. Why put a shroud on the US that is purely cosmetic? I thought the S510 shroud was to circumvent the need for a separate silencer which is illegal or needs to be licensed in some countries (notably some US States). The stupid idea is to fit the silencer to the shroud when the barrel is semi-floating... just my opinion... and then there's the length! :o

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patratel
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Re: S510 Classic with bad grouping

Thu Jul 09, 2020 5:00 am

Roger5 wrote:
Tue Jul 07, 2020 12:15 pm
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 that, but I did try with and without an AA silencer. From that I learned that you have to carefully align the silencer to the barrel, or else you destroy the grouping completely. But once the alignment is OK, grouping is just as good/bad as without silencer (only at a different (x,y) location on the target)

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patratel
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Joined: Tue Jun 30, 2020 4:35 am

Re: S510 Classic with bad grouping

Thu Jul 09, 2020 5:04 am

Roger5 wrote:
Wed Jul 08, 2020 10:59 am
I believe patratel is talking about tethered benchrest, in which case the reg is attached to the dive bottle and not in rifle.
It might be handy to know where he's based ?
You are right. I am talking about benchrest, but I am cheating a little now in the beginning, but putting the pressure regulator on the dive bottle and letting the pressure hose attached to the rifle while shooting.

I also tried with another, more fancy & expensive pressure regulator -- also on the dive bottle -- the one with two large pressure readers on it. It did not make any difference, besides the easier pressure setting.

I'm from Belgium, by the way.

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patratel
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Joined: Tue Jun 30, 2020 4:35 am

Re: S510 Classic with bad grouping

Thu Jul 09, 2020 5:12 am

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 now ever further away. I exclude the possibility of them borrowing me any scope.

My theory about the scope is that it could be the reason only if the glass plate with the target cross, which is in the image plane somewhere inside, would be able to shift up-down-sideways randomly; any other of the optics inside could only create some varying aberrations, if it would move in any direction.

So I'm waiting for the weather to stabilize a bit and will then go hunting/begging for a scope at the club.. was already on my list, but anyway.

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