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Thread: grouping changes on S400

  1. #1
    psychoSven's Avatar psychoSven
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    Default grouping changes on S400

    to all with an AA S400! does anyone find that their S400 changes groupings from day to day or if its been taken out of the gun bag! well i consulted luise( the AA importer) on this problem and his suggestion was probably my scope(hawke reflex 6x42), could also be something loose like the figure 8 piece holding the barrel and cylinder in place, the 2 grub screws could have been loose, but after tightening all the screws(the scope still remains the same), i found that the gun was doing the exact same. but on closer inspection i saw that the o-ring holdin the barrel on the figure 8 just never had a snug fit. do AA do this for safty and if so what would it prevent? well i baught a thiker o-ring and after some struggling i managed to get it to slide on, now its toit like a toiger and hassle free, groupings stay exactly where i left them the day before!

  2. #2
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    Nope, mines been 100% from when I first got it.

    Do me a favour though, what's the outside diameter of your barrel?

    ...

  3. #3
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    Well well ! I thought it was me ? Every time I take the weapon out , I have to re-zero , normally 2 clicks left or right , but still pisses me off .

    What " o ring " did you change pysco ?

    I see my plastic 8 piece is also a loose fit & I was wondering if that had some thing to do with the way ward zero !

  4. #4
    Marksman
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    Hi Gerry
    Try another scope for a while first before you blame the gun.
    If that does not cure the problem then try the thicker o-ring.

  5. #5
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    Hello Guido , I am using a borrowed Ultra tech 4 x 32 while waiting for my 30mm mounts ! I have a perfectly good Nicko nighteater to put on .

    This wayward zero , I though at first , I store the weapon barrel down in the safe , on a nice padded cussion , & I have a low wattage bulb burning continually in the safe . Living in Natal we have a certain amount of damp , & my hunting rifle leather sling used to grow mould . Since I put the bulb in there about 5 years ago , I have had no damp problems with any thing .

    I thought maybe the temp in the safe was causing the zero to drift like this when it was taken out , so for a few weeks it was stored in the wardrobe , same thing moving zero .

    On sunday arvie I was plinking in the front garden . Feeling a bit stiff & sore after racing in the Noodsberg Off road race . I shot about 50 pellets , had to reset the zero as is normal when I started , put the rifle down on the side , on a doubled over blanket on the table , went to respray the swingers & change the target paper . Picked up the rifle shot & was 2 bloody inches to the left ? ? ? 8 Clicks later was back on zero again , but I was pretty puzzled about it ? ?

    In the past I've looked at the figure 8 plastic support & wondered at the fact that it is completely loose over the barrel , but figured it was truly free floating ! !

    Today I look at the parts diagram & see that there is a " front clamp ring " no deatils other than that .

    I have no other scope other than a tiny BSA pellet gun scope 4 x 20 to try .

  6. #6
    Marksman
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    ok...sounds like a barrel to collar problem.
    Try and loosen the grub screws holding the collar to the cylinder and recenter it on the barrel..perhaps it is putting too much pressure on one side of the barrel.
    The barrel sits inside this collar and is supported by an o-ring to allow for movement when the cylinder expands with different fill pressures and temperatures.
    It is thus a semi-free floated barrel.
    I have never liked the barrel mounting on the S400 and unfortunately the barrel is too thin to be free floated.
    Perhaps also experiment with first a thinner and then a thicker o-ring supporting the barrel.
    They are easily available at dive shops or hydraulic outlets.
    Also I do not think it is a good idea to store the gun pointing down with all the weight on the end of the barrel.

  7. #7
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    I also found that my rifle has to sighted everytime I want to shoot. I asked the question loud enough at DD the other day and the replyI got was that it is normal as I have transported the rifle.

  8. #8
    Marksman
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    no its not normal and should not happen regularly...maybe if you really bump the rifle around....
    I seem to remember Casper had a similar problem..mmm

    Perhaps post the question on the British forum...there are thousands of S400 users there, I am sure they will help you.

  9. #9
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    Maybe try loosening the stock bolt. Might be a bit tight and moving around everytime you transport it. If it's slightly loose the action should relocate automatically.

    ?

    ...

  10. #10
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    Guido,
    did Casper own my old S400 ?
    I never had that problem when I sitll had the S400.

    There is ofcourse a very big possibility that it's the scope not holding it's zero.
    My advice for scope testing:
    Make sure that you only work with the turrets and keep gun movement to an absolute minimum.
    Zero at say 20m, shoot 5 shots,
    go 10-20 clicks left, 5 shots,
    go same clicks up, 5 shots,
    go same clicks rights, 5 shots,
    go same clicks down, 5 shots,
    Is the point of original zero still the same after all the adjustments ? If not it's the scope/mounts !
    If yes, now check the barrel collar/o-ring and all other screws ?

    "When you put cheap tyres on a Subaru don't complain about traction ..."

  11. #11
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    Looks like a proverbial can of worms has been unearthed here ! !

    Some how I dont think its a scope problem , no common scope & mounts being used here , suspect more a rifle quirk maybe .

    If any one finds any more info out regarding this , please post the info ,

    Thanks ,

  12. #12
    Sharp Shooter
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    Hi Guys,

    Having a wandering zero on an S400 is not normal. My own rifles never shift zero despite not always being used as regularly at the moment.

    Although it is a little difficult for me to make a diagnosis over the net, I will quite happily try to help when I visit South Africa in a few weeks time.

    I will be in the country from the 16th April unitl the 2nd May and I will post a cell phone number that I can be reached on closer to the time.

    BTW - although not related to this thread - I will be bringing a couple of scopes that are now surplus to my needs to sell:

    1. Simmons Competition Airgun 6-18x40 fitted with a multi-line reticle , good condition. I am looking for R750 for this scope.

    2. Tasco 6-24x40 - older model but in good condition suited to introductory level shooter (duplex reticle). Looking for R550 for this scope.

    Regards

    Dale
    <span class='smallblacktext'>[ Edited Mon Mar 07 2005, 04:17PM ]</span>

  13. #13
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    Hi Dale ,

    Yes please find out all you can about this wandering zero . I loosened the barrel collar & found that the stock retaining screw was very loose . I tightened it up a bit , difficult to know how tight to make it , how ever its now firm . I tightened the 2 colar grub screws a 1/4 turn each until they were tight too . I found if they are both loose & you tighten 1 all the way it does exert a bit of pressure on the barrel , thats why I stuffed about doing a small bit on each grub screw .

    I hope to be able to try it tomorrow arvie , then we'll see how it goes . If still buggering about , I'll have to try another O ring , the scope !

    Dale , where are you going to in S A ?


  14. #14
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    soz - double posted.
    <span class='smallblacktext'>[ Edited Mon Mar 07 2005, 08:33PM ]</span>

  15. #15
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    If I may be so bold as to offer some advice on dialing although I don't follow this route myself...

    Normal threads (all threads apart from ball-screw threads because the nut is adjustable) have what is known as back-lash in them. No way around this unless you want a turrent that you have to turn with a spanner.

    Now a scope's inner tube is moved about by the turret thread pushing a 'pole' against a spring leaf. When you change direction on the turret again, the distance moved will be less. Due to taking up the tolerance on the threads.

    Look it's not alot, but as the thread wears so will the amount of back-lash. Easiest way to cure this is to always turn the turret the same way when finalising the setting.

    Eg: Current setting is 15m, dial up for next target at 20m, next required setting is 10m, so dial down to 5m then up to 10m. So all your settings are dialled up.

    Anyways just a thought.

    ...

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