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Air Arms S410 regulator and modded hammer

Discussion in 'Anything Airgun Related' started by terry1001, Mar 25, 2014.

  1. terry1001

    terry1001 Major Poster

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    My first pcp rifle was an Air Arms S410 classic in .177 (pre anti tamper) which I bought about 5 years ago. This was a return to air rifle shooting after many years shooting full bore rifles and pistols (and shotguns), previously I had only shot spring rifles and pistols. I was pleasantly surprised by the accuracy, power and low noise levels. Just over a year ago I bought another rifle, this time a HW100KT in .22, and now had a spare rifle which allowed me the opportunity to experiment with the S410 to see if I could improve the shot to shot consistency and maybe squeeze a few more shots out of a fill so I did plenty of research and decided to fit a regulator.
    First stage was to fit a Robert Lane regulator and at this point I thought (hoped) that this would be the answer. The regulator has the effect of extending the sweet spot from maximum fill pressure right down to the set regulator pressure which for me was 100 bar which roughly doubles the amount of usable air. The result was an improvement in shot count and consistency but not as much as I had hoped so I looked into other options for getting the result.
    I looked at a lot of research that had been done and here I am thinking about the experiments thst Cloverleaf carried out showing that hammer bounce was responsible for wasting a lot of air and also posts I found on the AAOC forum where some members had made and installed 2 piece hammers and achieved good increases in shot count. Some of this had been done for FAC rifles and also for the S400 so it wasn't immediately obvious what dimensions would be applicable to my 12 ftlb S410.
    The 2 piece hammer consists of 2 concentric parts which slide freely over each other, after the firing valve has been opened the outer hammer tries to bounce back but hits the inner part (which the main spring bears on) and the inertia of the inner part stops the rebounding which would otherwise open the valev another 2 or 3 times, wasting air each time. After some trial and error I made a unit which looks like this:
    https://www.flickr.com/photos/96928706@N04/sets/72157642912047393/
    The inner hammer is made from phospher bronze and the outer from 304 stainless steel.
    Since full shot strings are likely to be about 100 shots and quite a few adjustments and changes seemed likely I decide to save time, air and pellets by putting some aluminium tube inside the air cylinder to reduce the volume. This worked well and I was able to fill to about 180 bar and run strings of 30/40 shots until the rifle came off the regulator. Once I had got a hammer which worked, in that it cocked and the magazine indexed properly, I put the rifle back to standard spec to carry out some tests. Since my air bottle only had about 190 bar in it I only filled to 180 bar, at all times the rifle had the regulator fitted and I used out of the tin pellets with no weighing.
    The regulated rifle produced a maximum spread of 42fps and a standard deviation of 9.25 which wasn't very special.
    With just the 2 piece hammer fitted the maximum spread was 21 fps with a standard deviation of 4.5 and a noticeable increase in shot count
    This seemed to be a big improvement in performance but the power was a bit too low for my liking, the 2 piece hammer is lighter than the original and seems to let less air through so I moved on to further changes intended to increase the power to normal levels. Without going into details of how this was done the areas to be investigated are the transfer port and the spring tension for the hammer and firing valve. Making these adjustments is covered in detail on Robert Lane's Youtube channel and, in general, I followed his recommendations.
    Initially these further modifications made little difference but some fine tuning, and checking with Bisley Magnums as well, has now got me to a point where I am ready to carry out testing with the full air cylinder. At the moment I am getting a maximum spread of 11fps with a standard deviation of just 2.7 and I expect (hope) that this will improve over a full string which I will do after I get my cylinder refilled. I may also batch sort some pellets by weighing them to see if that gives an improvement, the current results are well within the variation in pellet weights so it is possible that this could be worthwhile. Unfortunately all this testing is time consuming, especially for full strings with the cylinder filled to capacity.
    Hopefully I can get this testing done fairly soon and then I will post the results, if they start looking good I may even try with weighed and lubricated pellets :D
     
  2. Chippy1988

    Chippy1988 Busy Member

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    Sounds good mate, I like you have the ability to make or replace parts, but have very limited time. I use a s400 so im interested in your results. I also enjoy reading every one of your posts as they are very informative.

    atvb James
     
  3. audiguypaul

    audiguypaul Donator

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    Have you seen the anti bounce hammer Rob does for the 410 ?
     
  4. terry1001

    terry1001 Major Poster

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    Yes, after I'd bought the stuff I needed to make mine!
     
  5. audiguypaul

    audiguypaul Donator

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    Sods law that is
     
  6. Hoodster

    Hoodster Engaging Member

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    BUILD IT AND THEY WILL COME :D I've just fit a Robert lane regulator to my 410c haven't fired a pellet through the rifle with it fit yet waiting for the time and weather, so I found this post most timely thx.

    When you guys speak of Rob doing a 2 piece hammer do you mean Robert lane ?
     
  7. Akita177

    Akita177 The Absolute State of Britian podcast

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    Yeah if you buy the regulator and hammer at the same time you get them for a good price, he sells them on ebay i believe there are made by Robert Nicolson and Rob Lane sells them on ebay.

    Terry i have a Tench reg fitted to my S410 carbine it was doing 70shots from a 210bar fill, after fitting the Rob Lane hammer and some fettling im upto 85shots with 210bar in the carbine.
    There has to be around a 0.6mm gap between the hammer brass carrier and the valve housing mine is bigger then that to bring the power upto 11.6ft/lb with the venturi almost fully open apart from the point of the screw, my firing pot is screwed fully in and cut to 18mm and a stand off made from the off cut of the pot to the same hieght with 2 holes in the side, though the breather hole in the air clynder was origninal drilled for a 18mm stand off.
     
    Last edited: Mar 26, 2014
  8. terry1001

    terry1001 Major Poster

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    I think that the Rob Lane hammer is a slightly different design, do you know what materials are used for the 2 parts? The AAOC version which mine is taken from has an o ring (8x1mm) around the hammer guide to stop the central hammer part from hitting the valve body.
    In my arrangement the transfer port restriction is removed and I have opened the port (all the way through) to 3.2mm, the firing pot is split into its 2 parts and the long chamber removed. Hammer and valve springs can be adjusted to get the right balance. A suitable stand off piece was supplied with the regulator.
    Every stage was checked over a chrono working at relatively low power until I got the parts working together. This does require a lot of stripping, adjusting and rebuilding of the rifle so it's a good idea to have spare o rings etc to hand before starting. I've had to use my old valve as the new one refuses to seal and I ran out of patience with it, maybe at some point I will try and lap it into the seat.
    I'm looking forward to running a full shot string through it once I get my bottle refilled, even with using the inserts in the air cylinder I got through quite a lot of air. I know it doesn't cost much but I hate to waste any! At the moment I'm getting about 11.4 ftlbs with Bisley Magnums so I won't make any more adjustments until everything has settled in.
    What pressure are you getting from your Tench reg and what calibre is your rifle?
     
  9. ratman60

    ratman60 Very Active

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    hello, 210 bar fill?? how come when AA say 190 max, i find such interest in what forum members do with their skill and knowledge, oh i wish i still had my workshop!!!!
     
  10. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Very interesting (and nicely made) Terry.. I'd be interested to know a bit more about it all, such as:

    - The mass of each part
    - The striker stroke
    - Whether you're still using the original striker spring

    As I'm sure we've discussed previously; while this design of striker works reasonably to cut bounce, I think you'll suffer drawbacks in other areas - most notably lock time. Of course the valve will require less force to open since the (regged) pressure holding it closed is significantly less (usually 80-90bar) than that present in a "naturally aspirated" rifle (typical operating pressure of a well setup one 120-190bar, as I'm sure you well know) so you'll potentially lose a bit of lock time here as the striker won't need as much energy and momentum to open the regged valve. Of course a lighter / shorter-stroked single piece striker would be ever quicker (albeit more wasteful of air).

    I'd be very interested to get yor rifle hooked up to the listening gear (which would quantify the lock time, shot development time and number of instances of striker bounce) unfortunately you're a bit of a distance away, though...

    Anyway, will be interested to see how it progresses :)


    AA state a 190bar fill as this was the pressure that the original 300 and 400 series were designed to work at; a pressure defined by the operating characteristics of the valve setup. Now with their sh*tty, soft valve heads the ideal fill pressure might be as low as 140bar in a badly affected gun.

    I believe the AA air tubes actually state "200bar max"; they're designed to fail "safe" (the ends flare out) at around 250bar, and I suspect the bare tube used would probably endure double or triple this stated max before failing.. so there's no issue with filling to 210bar from a safety perspective.

    The only potential issues being that a) it's closer to the 250ish bar point where the cylinders go pop so you have less of a margin of error on accidental over-filling, and b) the higher pressure will exacerbate the extrusion problem with the soft valve heads..
     
  11. terry1001

    terry1001 Major Poster

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    At the moment Im considering this to be 'work in progress'. I've got to a stage where it seems to work as expected although that is still to be confirmed in terms of total shot count. So far I'm using an original 410 hammer spring with no modification and my next experiment is to add some preload to it to find out if this is beneficial. The new, outer hammer is considerably lighter than the original but so far I haven't weighed the parts although I will do that the next time I take it apart. At the moment I still have a persistent slow leak which I think must be through the firing valve which will have to be attended to, when the internal mods are sorted I will strip it and replace all seals etc.
    When it's all finished it will be interesting to work out whether it was worth the effort :D
     
  12. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Cool - will be interested to hear what everything weighs. Speaking of exhaust valves, I've just ordered a couple to my own design in Acetal (not sure how long they'll take) once I've tested them I'll be looking to get a batch made and disseminate them into the wild, if you're interested ;)
     
  13. Akita177

    Akita177 The Absolute State of Britian podcast

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    With low power i would guess the hammer isnt opening the valve stem enough, and im sure the oring wont be upto the job and eventualy your power will creep up as it wears.
    And with the pressure agaisnt the valve being at a constant lower pressure with the reg fitted i found screwing pot/valve spring all the way in increased air efficiency alot on mine.

    Ratman60 with a regulator fitted the firing valve has a constant regulated pressure typicaly 90-100bar so a higher fill pressure has no effect of the guns operation.
    210bar is considerd the safe max pressure by alot of gunsmiths including Ben Taylor for the S4xx.
    My Bro has filled his regged BSA Ultra to 280bar on a few occassions when shot count was needed, not that id recommed people do it.
     
  14. Akita177

    Akita177 The Absolute State of Britian podcast

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    Ive just scanned the set up instructions for the Anti Bounce hammer Rob Lane sells, guys PM me with your email address and i will send it you.
    I could post the scan here but dont wish to beak any power adjustment rules.
     
  15. Hoodster

    Hoodster Engaging Member

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    I've just bought one off flea bay (2 piece hammer that is) I will have to wait a while to see what kind of results I get.
     
  16. terry1001

    terry1001 Major Poster

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    UPDATE
    After a few distractions I have carried out some more checks on the rifle. The current hammer in use has an outer part which weighs in at 36.17 grams compared to 44.74 grams for the original, the phosphor bronze inner part weighs 18.68 grams. I have used the original mainspring and firing valve/firing valve spring.
    The first results seemed quite good and I set the power at about 11 ftlbs with AA Field to allow some leeway with heavier pellets, Bisley Magnums had previously been about 0.75 ftlbs more. The rifle is a S410 classic in 0.177 and the rifle is pre anti tamper although the actual date is unknown.
    The main benefit of a regulator is getting rid of the sweet spot and allowing the rifle to be filled to maximum pressure, theoretically with no velocity variations. I filled the rifle to 210 Bar and sorted out a batch of AA Fields which had been batch weighed, the ones I used were between 8.46 gn and 8.54 gn giving a nominal weight of 8.5 gn.
    Using a CB625 I set to and shot 120 pellets to get a shot string, after 105 shots the pressure had obviously dropped to the regulator pressure as shot 106 onwards showed a decrease in velocity. The graph of this is here:

    [​IMG] View attachment 96686

    One point that did seem slightly odd was a reduction in velocity which happened about shot 60, the average velocity from shot 1 to 60 was 771 fps dropping to 769 fps between shots 61 and 100. I drew a line after shot 100, being 10 magazines worth so an easy to remember number if I ever want to get the maximum from the rifle.
    Overall the result was, over 100 shots, a velocity averaging 768 fps with a standard deviation of 4.5
    the first 60 shots gave an average velocity of 771 fps with a standard deviation of 2.8 and
    the shots 61 to 100 gave an average velocity of 764 fps with a standard deviation of 2.6.
    Overall there's a quite usable 100 shots available from full which isn't too bad and there is still some scope for fine tuning. Bisley Magnums actuall give 11.2 ftlbs so there is some potential for a small power increase although I'm not convinced that an extra 20 fps muzzle velocity is worth much 40 yards downrange.
     
    Last edited: May 20, 2014
  17. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Good work :)

    I did write an essay on your graph but the sodding forum signed me out and I lost it all.. in addition (not sure if I'm the only one) but every time I try to view page 2 of this thread it crashes Firefox.. Perhaps something to do with the attachments? The page seems fine when viewed (begrudgingly) using IE.

    Anyway, in an effort to cut to the chase about your graph:

    I think the gradual decline in velocity over the charge is due to the reg cycling faster at higher cylinder pressures (due to the greater pressure differential across it); refilling the output chamber faster when cylinder pressure is higher, thus maintaining a higher mean pressure in the output chamber throughout the shot cycle at higher cylinder pressures and hence driving the pellet faster.

    I think your striker, port and reg are not perfectly balanced - notice how the velocity falls off sharply as soon as the gun comes off reg. Ideally, as the gun comes off reg the velocity should fall away in a gentle curve; just like the latter part of an unregged string.

    The valve gear in the gun should be setup so that, when operating without a reg, the pressure at which the peak of the velocity curve occurs (where the exhaust valve is operating most efficiently) is the same as the reg output pressure.

    If the reg pressure is lower than that at which peak valve efficiency occurs the velocity will spike as the gun comes off reg. If the reg pressure is higher than that of peak valve efficiency you'll get a sharp falloff at the end of the string - as seen on your graph. This is typical of a "N/A" gun converted to regged operation - a standard S400 should experience peak velocity at maybe 130-160bar; while for proper operation the reg requires this to happen at 80-100bar (depending on where the reg output pressure is set).

    This behaviour is inkeeping with my thoughts about the gradual velocity loss over the charge - consider how velocity is affected by changes in cylinder pressure at different points in the N/A shot string. Where the gradient of the velocity curve is steep (i.e. velocity is changing rapidly with respect to cyl. pressure) a small change in pressure will have a significant effect on output velocity.

    Now consider the region at the peak of the velocity curve - this represents a plateau over a period of maybe 10-15bar where changes in pressure have very little influence on the velocity. This is another reason why you want the vel. peak pressure to be the same as reg pressure; in a nutshell while operating as it is currently your valve gear is overly-sensitive to changes in reg output pressure; which is exacerbating the fact that the reg is providing a higher mean output pressure at higher cylinder pressures due to the faster fill rate of the reg.

    Correctly balancing the reg, valve and port will most likely level the velocity string right out; along with giving a much smoother transition period as the gun comes off reg.
    You can achieve this in two ways - either wind the reg output pressure up so that it's operating at the exhaust valve peak efficiency pressure, or reduce the pressure at which peak exhaust valve efficiency occurs by reducing the striker impact energy (short stroke, less spring preload).

    In reality you'll probably need to do a combination of the two; since increasing reg output pressure will increase velocity (although you have a bit of headroom there), while reducing the striker impact will reduce velocity. Larger transfer ports promote lower peak valve eff. pressures too - in a N/A gun at a given muzzle energy, the trend is basically: vel. peak at higher pressure - restrict port, Censored valve harder, vel. peak at lower pressure - open up port, reduce striker impact on valve.

    I hope this makes sense ;)
     
  18. terry1001

    terry1001 Major Poster

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    I've been contemplating the options for tuning the firing system to improve consistency and possibly the shot count, this first complete string gives some of the information about the current situation. I'm reluctant to make any significant change to the regulator output pressure which is set at 100 bar, as delivered, the transfer port has been slightly enlarged to 3.2mm.
    The areas that I'm thinking about are the hammer assembly/spring and the firing valve/spring although the two part hammer adds some complications. Unfortunately there doesn't seem to be an easy answer and it looks as though a considerable amount of trial and error is going to be needed.
     
  19. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Yup; such is the joy of regging otherwise unregged guns :p

    Ta for the posting the weights.. so your total striker mass is around 55g so around 20-25% heavier than the original (which will impact proportionally on lock time) while the active part is around 20% lighter than stock at 36g.. so you're already down on striker impact energy / momentum compared to the original setup.

    Is the transfer port wide open at the moment or is it restricted at all?
     
    Last edited: May 22, 2014
  20. terry1001

    terry1001 Major Poster

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    It's wide open and bored to 3.2mm which is about what is suggested by Robert Lane for the rifle. At the moment the springs are the originals from the rifle before fitting the regulator, I'm trying to not change too many things at once so that I have some chance of working out what changes work or don't. Wouldn't it be nice if there was a single dimensioned drawing showing all the answers!
     

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