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Another Problem S 410

Discussion in 'Technical' started by BLoBacK, Feb 13, 2019.

  1. BLoBacK

    BLoBacK Engaging Member

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    I was recently given an S410 to sort out for a friend. It was only doing 7.5fpe. The rifle is a pre - anti tamper model, manufactured in 2005. Altering the power adjuster made no difference so it was a case of stripping the whole rifle to try and find the fault. Straight away I found the firing valve to have succumbed to the dreaded valve creep so a new one was ordered. While it was in pieces I polished the hammer shaft . The hammer itself looked brand new. I,ve re-assembled the rifle after setting the valve pot to the recommended 57mm. I also checked to make sure the barrel hadn,t turned for whatever reason, blocking the transfer port. I,ve tried the tissue paper test over the breech assembly and, no leaks. But the rifle still won,t go above 10fpe, no matter what I try. I was using AA field pellets. Any suggestions folks?
     
  2. robs5230

    robs5230 Pro Poster

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    Fill to 150 bar and test with JSB heavy, which will hopefully show an increase.
     
  3. Bezzer

    Bezzer Engaging Member

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    With what you've done new valve, cleaned the hammer rail checked the transfer port etc the only extra thing that could really be checked would be the hammer spring, has it goosed itself after 14 years?. It should be 63mm/2.5" free length. Unfortunately there's next no room to stick a spacer in to try it, 2 or 3 mm and it won't cock. You really need a similar spring to see if that's the problem.
    Other than that just make sure it's in its sweet spot 110-170bar, if it's overfilled the power will drop.

    Just remembered something- has it got an OE sized 6x1 O ring between the upper and lower receiver transfer port holes not an oversize one? Some owners put a 1.25 or 1.5 there instead which if you really clamp down the fixing screws can obstruct the port. Should never need anything but the OE one, the upper to lower fitting tolerance is spot on and doesn't need extra.
     
  4. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    To expand on / counter this point the tolerance on these parts isn't always spot on and can result in the 6x1mm O-ring getting sucked down the transfer port and shot out of the barrel upon firing (yeah, I know - I wouldn't believe it either unless I'd experienced it numerous times), which will obviously drop energy so it's worth checking that the original seal is still present.This can be remedied by fitting a fatter section O-ring as you describe - I've had consistant success with 5x1.5mm ;)

    Also, OP - are you sure that you're adjusting the port and not just a backup / cover screw? Exhaust valve moving freely within its bore? Bit of an odd one tbh!
     
  5. Bezzer

    Bezzer Engaging Member

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    Never seen a sucked in O ring must not have been seated right in the first place. But have seen spatters of silicone around a thicker ring that wasn't fully sealing, threads wouldn't have been far off stripped to get it fully clamped down and a flattened thicker one that would have been causing an obstruction. The way I look at it is the gun originally came with an OE one and was OK then why should it have changed in the meantime?, there is no wear to take into account.
     
  6. Roger Archbold

    Roger Archbold Engaging Member

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    Just done an S510, the guy wanted the reg removed and returned to standard, it was an altaros so cylinder not drilled, set firing valve to 57mm filled to 165bar 1st shot with AADF 8.4 was 7.5ftlb reset firing valve 2nd shot 9.48ftlb reset again 14.60ftlb more playing about, now doing 11.51 the S510 is slightly different to S400/410 as there is a spring guide inside the pot, so 57mm appears to be close but 58.5 might be nearer, if your wondering, I prefer to adjust firing valve instead of using Venturi screw, it does take a bit longer though
     
  7. BLoBacK

    BLoBacK Engaging Member

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    I tested the rifle at 140, 150, 160 and lastly 180bar which predictably, dropped the power down to 9.7fpe. The rifle had obviously been tampered with because the gauge manifold was leaking due to having been fitted with the wrong 0 rings. And, some of the screws were chewed up. ( don,t you just love it when people mess with things of which they know nothing?). The TP cap screw was also missing. I have fitted the nearest I can get to the transfer O ring , a 5.4x1.4 one.
    Latest finding . I have just removed the barrel ( one of those screws was also fu-bard ) and found that the thin o ring that seals the brass sleeve and the barrel is missing. I,ll test it again tomorrow. I,ll keep you posted.
     
  8. BLoBacK

    BLoBacK Engaging Member

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    Well I fitted a new breech o ring and loctited the brass sleeve to the barrel. I also fitted an oring to the barrel and actually found and fitted the correct TP o ring. result? 11.3fpe at 170 bar. Happy with that.
     
  9. Victor Robert Allaway

    Victor Robert Allaway Engaging Member

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    Not a bad result for the price of a few o-rings, unless you have to factor in your time. Sometimes it can be a pleasure, even repeating yourself as you increment the adjustments, other times it can really grind you down! It does go to show that the AA design is pretty much bullet-proof, though. But it's a pity the exhaust valve has to be considered a consumable item.

    Rob.
     
  10. rhogg4794

    rhogg4794 Member

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    My S410 after nine years sucked in it's oring so I disagree with you there. I think after years the rubber naturally hardens and shrinks a tad. I replaced all the o rings and it's good to go for another nine years, I hope.
     
  11. BLoBacK

    BLoBacK Engaging Member

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    Whilst i,m a huge fan of Air Arms rifles ( I own an S510 and a TX200hc), I still think they could be improved to make them more maintenance friendly . Firstly , that firing valve. I,m sure they could make it out of a material less susceptible to creep. On my old S410 , which suffered creep , I made a new valve from Delrin. Problem solved. Secondly, that tp seal . A circular recess into which the oring would sit would cure the sucking down the tp problem. And, lastly , why do they they put the pot locking screw underneath the gauge manifold ? Just a few degrees off centre would make things easier. For the record IMO Air Arms still make the best out of the box airguns. Just saying :rolleyes:
     
    Pete236 and pbrown like this.
  12. Bezzer

    Bezzer Engaging Member

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    Dunno about being more maintenance friendly they are some of the easiest guns to work on and there are no hard to find or expensive seals.
    The firing valve doesn't "creep" if it did it would be leaking, it just grooves lowering the power. Time will tell on your delrin one, when I made one in that and a load of other plastic types they didn't last that long, certainly nowhere near an OE one, Peek might be the closest to the hardness of OE unfortunately my 2 are regged so I can't get the pressure to get the initial seal/forming with it.
    There is a slight recess for the TP O ring, a smear of silicone grease will keep it in place no problem while it's reassembled, the only reason for it getting blown out, which I've never seen, is not taking enough care on reassembly. If the rubber fails then maybe, but as said it takes years to perish and obviously not checked/serviced in that time.
     
    pbrown likes this.

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