Air Arms barrel band.

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RichieRich612
Posts: 125
Joined: Fri Apr 19, 2019 2:02 pm

Air Arms barrel band.

Mon Sep 09, 2019 1:36 pm

What's the best way to ensure the barrels perfectly aligned when tightening up the figure of 8 barrel clamp?
Rich

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Roger5
Posts: 866
Joined: Sat Jul 25, 2015 8:04 am
Location: Hampton middlesex

Re: Air Arms barrel band.

Mon Sep 09, 2019 4:45 pm

Ive never had a problem with the barrel band, I just loosen the grub screws and let the barrel sort itself, if it's a problem, you can fit a rowanengineering one, and you can see a gap all around the barrel, just tighten when it's not touching, fitted one on my S400, kind of floating without the worry of knocking and maybe bending the barrel

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rob2hook
Posts: 28
Joined: Sat Jul 21, 2018 10:29 am

Re: Air Arms barrel band.

Mon Sep 09, 2019 5:06 pm

There is an AA video on their YouTube channel showing realignment on a stepped jig. I guess this has proven adequate to make the rifle more accurate than most shooters, so you can understand why no greater expense is wasted during manufacture. The method shown might be improved by making it two-handed with one holding the gun on the jig whilst the second torques up the screws in the barrel band.


There a number of issues as to quite what one hopes to align to what. given the number of joints from the cylinder (being used as the datum) through the firing valve body, into the breech block and then to the barrel how would one know if this is the correct alignment for best performance? Indeed, surely it is only really important that the barrel should be in as near perfect alignment as possible to the scope rails, not the air cylinder - and I can't think of a practical way to test this!

I rather like the suggestion, seen elsewhere, that the band should be removed and the sights zeroed with the barrel free floating. With the band refitted, tinker about until the POI is correct, at least in the horizontal plane. If there is a difference in the vertical plane, then I doubt it could be corrected. Bear in mind that the barrel is held in place by two grub screws along the top of the block (and perhaps some errant Loctite), which is less than optimal for alignment. Ideally there should be a pair of screws at each end of the joint set in a vee (like on the barrel band) so as to ensure the barrel to block contact runs along the bottom of the joint throughout - but it all works in practice.

Rob.

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Archer50
Posts: 179
Joined: Mon Jun 20, 2016 5:06 pm
Location: Perth

Re: Air Arms barrel band.

Mon Sep 09, 2019 11:09 pm

Roger5 wrote:
Mon Sep 09, 2019 4:45 pm
Ive never had a problem with the barrel band, I just loosen the grub screws and let the barrel sort itself, if it's a problem, you can fit a rowanengineering one, and you can see a gap all around the barrel, just tighten when it's not touching, fitted one on my S400, kind of floating without the worry of knocking and maybe bending the barrel
I agree, you don't centre the barrel, you let the barrel centre itself.

If you try to force it into what you think is centred, then make it stay there with the barrel band, you are unlikely to get good grouping because of the peculiar barrel harmonics this will cause, and you will probably get big shifts of POI with changes of temperature and cylinder pressure. Also, as Rob says, a lot of apparently off-centre barrels are actually off-centre cylinders and the AA alignment jig is just a quick way to make a less-than-perfect gun look presentable for sale: I'd avoid it, or anything similar, like the plague.

If the barrel really is so off-centre it has any practical effect, then the barrel or its mounting in the action must be sorted rather than trying to force everything into line with the barrel band.

Alan

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rob2hook
Posts: 28
Joined: Sat Jul 21, 2018 10:29 am

Re: Air Arms barrel band.

Fri Sep 13, 2019 10:26 am

Yes, I guess that's a more direct and concise way of putting it The barrel band is not there to position the barrel, just to support/protect it against outside influences.

Rob.

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