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

A tale of two power curves

Discussion in 'Anything Airgun Related' started by mark112, Mar 5, 2014.

  1. mark112

    mark112 Engaging Member

    Messages:
    335
    Likes Received:
    3
    Location:
    Coventry
    Hi,

    This is a power curve from my .22 S410K:-

    View attachment S410CarbineV2.pdf

    The orange lines represent a velocity difference of 1.5% of maximum. The yellow line is 2.5% As you can see 65 excellent shots at the top of the curve (1.5%) or 89 goods shots available (2.5%). 19Fps total variation from filled (190bar) to empty over a total of 98 shots. This I am very happy with as I think this is quite a flat power curve with most shots perfectly usable. I am leaving this gun alone!

    This is the one from my .177 S400 Classic:-

    View attachment S400ClassicFull_190fill.pdf

    Again the lines mean the same thing but this time 52 shots fall within the 1.5% region and 82 within the 2.5% area. There is a 50 Fps difference across the fill range (190 to 95 bar) with a total of 158 shots.

    Both rifles have new valves, hammer springs and valve springs and have a pot adjustment figure of EXACTLY 57mm. Power levels have been adjusted by venturi to 11.5 in the .22 and 11.2 in the .177

    Now my question(s) about the S400 Classic:-

    1. Is this a normal curve for a .177?

    2. What can I do (without parts modding just adjusting pot, venturi, mainspring preload) adjustment wise to make more shots available within the 1.5 and 2.5% brackets and thus make it more like the curve of my .22 S410k? It looks like I need to turn my graph clockwise. I'm not looking to keep the 160 shot total as half of them are not really usable anyway.

    3. Am I realistic in trying to get 100 shots within 2.5% and say 75 shots within the 1.5% bracket?

    Help me AirgunForum members. You're my only hope!

    Mark
     
  2. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

    Messages:
    19,714
    Likes Received:
    22,669
    Location:
    Oxfordshire
    Without writing an essay on the subject.. :p

    The .22 k's graph looks like a typical, well-setup example; it appears that the ideal (1.5%) fill pressure is around 170bar and the peak velocity occurs at around 120bar (what was your refill pressure?). This is very similar to the performance of my own rifle; the only difference being that your fill pressures all seem to be a bit lower than mine (which also gave around 65 shots but from around 190bar fill). What pellets are you using?

    As you say the .177 c's graph ain't so good - consistency is worse and the curve is very pronounced. I'd guess that your ideal fill is around 155bar and that the peak velocity is around 125bar. This clearly isn't great performance.. it's interesting to note that while the ideal fill pressure is lower than that of the .22, the peak velocity appears to occur a bit higher up the range.

    A few thoughts.. it appears that the .177 likes a fill pressure that's too low. This may be due to the infamous valve extrusion problem (how long ago was it replaced / could it be a particularly soft example?) or something else that will reduce valve duration - contamination on the striker rail or exhaust valve, binding etc. Another thing to consider is your choice of ammunition - I assume you're putting 8.4gn JSBs through it - heavier pellets (JSBs or Daystates) will give more efficiency and more shots per charge... obviously you have to balance this against their exterior ballistics though.

    If this is the rifle you had from me, it's already had some attention.. if you fancy having it to bits again though, I'd inspect the exhaust valve for extrusion (and replace again as nec.), polish the valve stem and check for free movement in the valve block, polish the striker guide rail, clean the bearings in the striker and run it all dry. Put a 2mm spacer on the striker spring and wind in the screw that cannot be named to compensate. It might also be worth checking the transfer port and breech seals to rule out any leakage. Run it over the chrony again and let us know how you get on ;)

    As much as I like .177, I've always found the 400 series to be more consistent and generally better behaved in the larger calibre..
     
  3. mark112

    mark112 Engaging Member

    Messages:
    335
    Likes Received:
    3
    Location:
    Coventry
    Hi,

    Thanks for reading my post Mike. It is indeed the gun purchased from yourself and above all else I will say that it actually shoots very well. My post is mainly due to poor weather I have had time to strip the gun and do a bit of work on it. Predominantly for my own peace of mind and also to improve performance (I'd hoped).

    Work done includes Hammer rail polish (although pretty good to start with), replace the two hammer bushes as I thought that the old ones had a bit too much play and may give 'chatter' (bit of a pain to remove but I got there :)). Hammer now silky smooth as per my S410k and runs dry also. New hammer spring, valve spring and valve 2 months ago. Did polish the valve stem as it was a gnats tight .. now will fall in under it's own weight. New seals fitted throughout.

    Basically this is what I did to my S410k to transform it but has not made much difference to the S400. Will try the 2mm spacer idea and adjust to suit. Pellets were 8.4 grain AADFs. Some of the spikes on the graph could be down to some of the pellets which have been in my shooting jacket pocket a few times and could have slight damage.

    What figures should a sorted S400C give shot count wise?

    Is there such thing as a very small air cylinder that can be used for testing to avoid wasting so much air or has anyone tried the method of testing with a lump of delrin/nylon/steel/aluminium in the reservoir. It is the power curve I am mainly trying to sort out first and if can do that over a 40 shot string it would be quicker. Any thoughts anyone?

    Thanks

    Mark
     
    Last edited by a moderator: Mar 6, 2014
  4. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

    Messages:
    19,714
    Likes Received:
    22,669
    Location:
    Oxfordshire
    No problem :)

    Sounds like you're most of the way there with the work you've done.

    Tbh I can't speculate from experience as to what a decent .177C should do; since I've not had one to bits since I discovered the valve issue. I have an early K with a Nylon valve that I believe gave 60 good shots (1.5%) from 200bar when I last tested it; so scaling this up to the larger C cylinder capacity would suggest around 85 good shots. This was an exceptionally good one though.. on the other hand the longer C barrel will aid efficiency slightly - I'd consider around 80 to be a good target.

    In .22 I've had a projected 75 "good" shots from a .22K, and around 105 from a .22C.

    I use an early TDR cylinder for testing - this is 200mm long / 95cc as opposed to the more usual 300mm/155cc (later TDR, K), 400mm/215cc (C) and 520mm/290cc (Extra) cylinders. On a .22K you can gauge the whole shot string over 50 shots, then scale up the shot count by 1.64 for a Carbine or 2.27 for a Classic. It works well, although a little less volume would be ideal.

    Will be interested to hear how you get on ;)
     

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