1. The Forum Rules have undergone some minor changes and updates.  Please take the time to read them; it will only take a couple of minutes of your time. By doing so, you lessen the chance of incurring the wrath of the moderation team or making yourself look foolish to other members.

    90% of users posting adverts in the Sales forums need to be reminded to read the rules as their posts are wrong.  This is unnecessarily time-consuming and will no longer happen - if your advert doesn't follow the Sales Rules it will be deleted and you'll have to start all over again.

    To close this box once you've read it (and the Rules), click on the X in the top right-hand corner.

    Thank you.

    AGF Staff



    Dismiss Notice
  2. A reminder of one of the Forum Rules:

    'Behaviour

    Do not make inappropriate or offensive posts - including threats, harassment, swearing, prejudice, defamation, deliberate insults or name-calling, other negative remarks about this forum, its moderators and administrators or your fellow members. Even if this is just your own personal opinion, RESPECT YOUR FELLOW MEMBERS.'

    There have been changes made to our censoring software in an attempt to help with this growing problem.

    Click the X in the top-right-hand corner to dismiss this notice.
    Dismiss Notice
  3. Dear members,

    Our membership (like our country) consists of people from all walks of life; different in far more ways than can be listed here and each with a different view based on their experience of life - regardless of their colour, religion or cultural heritage. Every single person in the UK has been born of mixed race – we are a multi-coloured and multi-cultural country.

    As many of you are aware there are a handful of individuals amongst this membership that persist in making provocative, inflammatory, racist and otherwise offensive comments. This has been happening across the forum to a certain degree but is most especially prevalent in the Adult section.

    The moderation team has tried to stay on top of this, however unfortunately because of the ‘offensive’ nature of much of its content we don’t monitor the Adult section quite as much as perhaps we should. As a result much of this behaviour has gone unnoticed unless it has been reported to us. While the team always intended to take a "light touch" approach to the Adult section it would seem that some people aren’t quite adult enough to be left unmonitored after all.

    This behaviour is, and always has been against Forum Rules as well as the specific stipulations of the Adults forum and it will no longer be tolerated. We feel it's time to draw a line in the sand and as such from this point onward offenders will receive an immediate and permanent ban from the forum.

    In order for us to achieve our goal of restoring the forum to the friendly and tolerant place it once was, we ask that ALL members be mindful of the content they post and help us to stop unacceptable behaviour by using the 'Report' tool at the bottom of any offending post - the results of which can be seen only by Admin/Moderators.

    You should all receive a copy of this message by PM. 

    To close this message box, click on the 'X' in the top-right-hand corner.

    Dismiss Notice
  4. Hotmail block emails from us entering your inbox. Unless you can setup a safe sender you will not get activation emails from the forum. Please use an alternative provider or complain to Hotmail.
    Hotmail addresses include.

    @Hotmail.co.uk @Hotmail.com @outlook.com @Live.com
    Dismiss Notice
  5. Postings on Politics, Religion & Controversial Off-Topic Material

    The majority of users do not want to read about these subjects and people have left the forum as a result of it – this is after all an 'Airgun' Forum. It’s all very well to say they don’t have to read it if they don't want to, but as most of us use the ‘New Posts’ button there is no easy way to avoid it.

    All AGF staff members are in favour of people being able to discuss what they want, but we have to draw the line somewhere if it is upsetting other users. We don’t want to read about these topics either.

    IMPORTANT- The discussion of politics and religion is no longer allowed anywhere on the forum (including the Adult section).  The only exception is if it's airgun related - they must be put in the Airgun Related Politics section..

    We will not tolerate bullying or personal attacks, racism or any other offensive 'isms'. we will remove these topics from the forum, we will not give you an area where you can abuse each other. We will not hesitate to ban offenders.

    To clear this text box, click on the 'X' in the top right-hand corner.

    Dismiss Notice

air arms chrono results strange ?

Discussion in 'Anything Airgun Related' started by Ganton Gunner, Jul 27, 2014.

  1. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    I did some strings with my air arms today im hoping you can help me with my results both guns set about 11ft lb

    s400 SL carbine in .177
    it does 90 shots from 200bar to 100bar 40 ish in sweet spot but about 50 ish useable

    s400 classic full length .177
    it does 50 shots from 200bar to 100bar all 50 useable no noticeable power curve till drops below 100 then it falls off quick
    no reg fitted and a lot of duplicates and some 2nd duplicates
    the attached string for the classic was at about 10ft lb I turned the power up a little after but deleted that string by accident 1st 4 shots was me adjusting power

    s400 SL carbine
    View attachment 100350
    s400 classic full length
    View attachment 100349
     
  2. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    both were filled to pressure using the bottle gauge etc and both used same pellets etc

    please note both graphs shown are from 200bar down to 100bar
     
    Last edited: Jul 27, 2014
  3. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    See cloverleaf's Air Arms exhaust valve sticky. I reckon the classic has a valve deformed which is why you are seeing less shots from the classic as opposed to the carbine. Still a very consistent shot spread though. Funny thing the Air Arms valve. You would think something so simple wouldn't cause such odd performance variations between guns but it does.
     
  4. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    if that's a faulty valve I think AA should make that standard :roflmao:
     
  5. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    just looked at cloverleaf's thread that does not match what is happening to my gun
     
  6. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    It's so flat it almost looks regulated but there is a slight curve towards the end of the shot string which is very similar to the problem cloverleaf was investigating. Power was down and you have said yours was only putting out 10ftlb ish in that graph, the number of usable shots was down (you should get another 20-30 shots from a classic over a carbine cylinder) plus peak power occurs much further down the fill range than would normally be expected. It all seems on the surface to be similar but as yours is so flat it looks unlike cloverleafs graph. It would be interesting to see the string at the higher power level and whether the shot count was down and the curve more pronounced and further down the shot count. Still I wish my 510 had a curve that flat and you're not wrong if they could produce that as standard at over 11ftlb it would be great.
     
  7. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    as stated in my original post but I deleted the string :( I turned it up to just over 11ft lb and same just a lower shot count closer to 50
     
  8. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

    Messages:
    21,829
    Likes Received:
    30,107
    Location:
    Oxfordshire
    Looking at the Carbine graph it looks like the velocity peaks at shot 65; which (assuming 1.1bar/shot average) corresponds to a pressure of around 200-(65*1.1)=128.5bar.

    Assuming a max allowable velocity variation of 1.5% of max over the string (in this case 0.015*784 or around 12ft/s), this makes the lowest acceptable velocity 784-12=772ft/s; the first acceptable shot based on these criteria (discounting a few low ones) being shot 50 at around 145bar and the last being shot 76 at around 115bar; giving 27 "good" shots. Discounting the highest velocity of 784ft/s doesn't give many more shots.

    From this information I'd suggest that this gun is showing signs of exhaust valve extrusion - giving under 30 "good" shots from an ideal fill of around 150bar. An example with no valve issues should give more like 45 "good" shots from a fill of 190bar. From the figures I'd expect the gun to be maybe 3-4yrs old.


    The Classic is the really odd one; obviously for a start it's running a little under-power; assuming an average velocity of 735ft/s with Exacts gives a muzzle energy of around 10.1ftlb. This (which will flatten the velocity curve considerably), coupled with the fact that the string is only 50-odd shots may suggest that there is a curve present; it's just disguised by the fact that it's stretched and the sample size is relatively small.

    Another point of note is that the velocity fluctuates markedly during the otherwise flat-ish string; perhaps suggesting an area of inconsistency in the rifle somewhere - for example a dirty or poorly-finished striker guide rail.

    In addition, if the fill is from 200bar the velocity drops off very quickly after only 50-odd shots. This implies that the rifle likes a high fill pressure (which will be the case anyway to some extent if the lower muzzle energy is the result of the port restrictor being wound in); in addition this behaviour would be characteristic of a very good exhaust valve - i.e. a pre-dog-Censored-soft white Nylon example - what serial is the rifle? If it's owt before about 045xxx or thereabouts it will have the better, earlier valve.

    If you discount the odd rising / falling trends in the string it's feasible to think that you're actually just seeing the latter part of a fairly flat shot string that wold have an ideal fill of over 200bar. The only final thing that confuses me is that those shots were over a 200-100bar - that's a lot of air useage (nearly 2bar per shot; a normal classic is usually more like 0.6bar/shot) which implies a leak somewhere - have you checked that the transfer port seal and breech seals are still present? Some guns have a habit of inexplicably blowing the tport seal out from beneath the breech and down the barrel..

    So, in summary; I'd check the presence of the two seals, check the colour of the valve (or just give me the serial and I'll tell you what it's most likely to be), inspect / polish the striker guide rail, wind the port restrictor screw out to give around 11.1ftlb with the Exacts (I find at this energy it's still legal with Heavies) and restest from 200bar ;)
     
  9. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    Yes I did see that, shame but you can't stop wishful thinking. It does sound similar to cloverleafs post as the shot count is low for a classic as you should match the carbine easily for number of shots. Although the useable shots are similar the carbine is giving more shots overall and it should be the other way round. Have you had it from new? Or has it been played with by someone else? The airarms valve is so simple it's laughable and very similar in function to the Sheridan valve on some paintball guns, spring rates could change performance on them without altering the venturi port size. You may have a weak hammer spring or over powered valve spring as opposed to the valve being deformed. Trouble is the only way to find out is to take it all apart and inspect the valve, reset the pot height to whatever it needs to be for the calibre and replace the springs. Depends how much time and testing you want to do. Or are you happy with the flatish curve and reduced shot count. If it is meeting your needs then you may as well leave it alone unless the shot count drops more. Either way it looks good apart from the shot count. Take a look at the exploded diagram for the valve assembly in the owners manual and you will see what I mean about simple design. The only place it can lose power after the valve is from the transfer port o ring or the breach seal but they would not affect shot count, that would only be affected by the valve head and springs as long as everything else is factory standard. Having rebuilt my sons .22 s400 valve assembly recently I can guarantee there is not much there that can go wrong ( I only rebuilt it because I broke it).
     
  10. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    I see Clover also commented as I was typing
     
  11. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    Having just fully read Cloverleafs post and not having looked too closely at the carbine graph I would be inclined to agree with him there. My 7mth old .177 carbine will come on power after about shot 15 and drop off from around shot 60 from a 190 bar fill. Where as yours come up to power at around 60 and then drops off quickly. The whole thing fascinates me as much as it does Cloverleaf. Unfortunately I just don’t have the time to devote to testing that he has put in (plus the wife would kill me if I did).
     
    Last edited: Jul 27, 2014
  12. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    yep the carbine I agree is extruded
    its just the classic that fascinates me as it is just erm weird lol anyway its in pieces at the moment and on internal inspection it has already been polished etc
    tp seal was missing but that still does not explain 50 shots from 200bar to 100bar
     
  13. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    It was probably low on power because of the missing seal so if you dialed it up it would use more air to overcome the loss giving less overall shots. Be interesting to see what it does after you replace the seal.
     
  14. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    tp seal replaced and breech seal too
    also replaced cylinder seal
    shot from 200bar to 105bar with adjuster screw wound right out
    View attachment 100364
     
    Last edited: Jul 27, 2014
  15. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    Now that is different. Plus is it my eyes or is there a 200fps drop in velocity.
     
  16. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    very different and yes a drop and the strangest string ive ever seen
    just opened it up to look at the pot
    not sure that's meant to be able to just slide off like that but it just slips on and off easy :(
    im guessing ive maybe found my problem
    View attachment 100365
     
  17. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    No its meant to be glued together as one piece. You seperate it like that and discard the part without the thread when you fit a Robert Lane regulator. If the pot is moving apart it will definitely affect the power as the spring will not keep the same tension on the valve. Very strange indeed.
     
  18. mattyts

    mattyts Donator

    Messages:
    6,201
    Likes Received:
    163
    Location:
    Yorkshire
    Has the previous owner been tampering with it Pete?
     
  19. Chinnymonster81

    Chinnymonster81 Busy Member

    Messages:
    544
    Likes Received:
    3
    Location:
    Essex
    Kinda looks that way doesn't it. Still a brand new pot isn't expensive if it won't bond back together properly. Gotta be bloody annoying for him though.
     
  20. Ganton Gunner

    Ganton Gunner Super Duper Moderator Staff Member Mod/Admin

    Messages:
    12,842
    Likes Received:
    103,330
    Location:
    Ganton scarborough
    spring is not standard either :( its a harder spring that's been cut down to fit in and ground off
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice