Results 1 to 14 of 14

Thread: Question about PCP air efficiency.....

  1. #1
    Sharp Shooter
    Doctor BAM

    User Info Menu

    Default Question about PCP air efficiency.....

    A method to work out your air efficiency was described on the Yellow Forum a while ago and I think it is good to repeat it here....

    Bar-cc/fpe = [(reservoir pressure change, Bar)*(reservoir volume, cc)]/[(#shots taken)*(muzzle energy per shot, fpe)]

    Any PCP can be evaluated according to its properties by using the factors mentioned above.... Reservoir volume, shots taken and muzzle energy all play a role, so that efficiency can be measured relatively....

    Indicator values for PCP rifles only

    For the .177 calibre, a value of 12 or less will be good....
    For the .20 calibre, a value of 13 or less will be good.....
    For the .22 calibre a value of 14 or less will be good....

    Assuming the Crosman Discovery values for a .22 is as follows :-

    Charge pressure 2000 psi (137 bar), recharge at 1000 psi (70 bar)
    135 cc air tube, 35 shots at 22 fpe
    Efficiency rating is 11.75 and clearly better than 14......!!!!

    Same rifle in .177 calibre with 28 shots at 16.5 fpe
    according to Gaylord's article...
    Efficiency rating is 19.58 and clearly not as good......!!!!

    Comparative values for the BAM B-51 in .177 is :-
    Charge pressure 160 bar down to 110 bar
    Reservoir volume is 196 cc
    Number of shots easily 45 useable at 22 fpe
    Efficiency rating is 9.9 and way better than 12 stated as the average....!!!

    Let's get those figures out in the open for all to see.......

    malan
    Sign Up To Air Rifle SA Forums

  2. #2
    Sharp Shooter

    User Info Menu

    Default

    what do you define as useable shots?
    Sign Up To Air Rifle SA Forums

  3. #3
    Sharp Shooter
    Doctor BAM

    User Info Menu

    Default

    A variation of not more than 10 ft/sec in 12 fpe rifles and not more than 20 ft/sec in 22fpe rifles....
    The value relates to when you see a deviation in your vertical POA when you shoot your useable shot string at 45m....

    malan
    Sign Up To Air Rifle SA Forums

  4. #4
    Sharp Shooter

    User Info Menu

    Default

    How much deviation at 45m?
    Sign Up To Air Rifle SA Forums

  5. #5
    Sharp Shooter

    User Info Menu

    Default

    This might be an indication of efficiency but not a very good one.

    The valve of your rifle(unregulated) runs more or less efficient at different fill pressures. Thus for the same rifle you will get a different efficiency index depending on how many shots you take into account.

    For my S400 I can take either 136 shots that I would use in competition with a lowish ES or about 200 shots with a higher ES but would be perfectly acceptable for me when I am out hunting up to 40-45m. For the different cases using the same rifle I get about 10.3 and 10.6 respectively. (this is without any tuning done to the specific rifle)



    Sign Up To Air Rifle SA Forums

  6. #6
    Sharp Shooter
    Doctor BAM

    User Info Menu

    Default

    Arnold
    I am not trying to re-invent the wheel here.... I just wanted to illustrate how to compare efficiency.... Your calculation of 10.3 to 10.6 is good compared to the norm of 12....
    If it had been 19, as in the case of the Crosman Discovery, I would have been worried.... The formula just goes to show how easy it is to mis-interprete figures when trying to compare efficiency.....
    If you think it is not a very good way of comparison, then please come with something better.....!!!!!

    malan
    Sign Up To Air Rifle SA Forums

  7. #7
    Sharp Shooter

    User Info Menu

    Default

    The only point I was trying to make is that the method is not that accurate. Although a good indication it should only be used as that and not for strict comparison of rifles.

    Remember your BAM has been tuned. The S400 has not been optimized for shot count yet. The discovery has not been tuned and it is catering for CO2 aswell. This makes it difficult to optimize the firing valve for efficiency. You might find that the efficiency is very good when using co2 in the discovery.
    Sign Up To Air Rifle SA Forums

  8. #8
    Sharp Shooter
    Doctor BAM

    User Info Menu

    Default

    Point taken, let us see when Gaylord tests the rifle in CO? style....
    The values given as 12 for the .177 and 14 for the .22 calibre is for compressed air only and cannot be used for CO? comparisons....
    The design of the valve has to change drastically between CO? and compressed air because of the difference in flow rates....

    malan
    Last edited by malan128; 22-05-08 at 15:57.
    Sign Up To Air Rifle SA Forums

  9. #9
    Protea FT Team '08

    User Info Menu

    Default

    Malan , i also was barking up this tree with my s400 and wanted to get a regulator.

    Dale gave me some advice that more or less came down to air is cheap is it worth it ?He makes a good point.

    If I worked it out my S400 has a 8.9 rating
    Sign Up To Air Rifle SA Forums

  10. #10
    Sharp Shooter
    Doctor BAM

    User Info Menu

    Default

    Allan
    Those are very good figures for the S400 and I am not surprised, because it is a very good design to start with.....
    One must try and evaluate your rig according to the norm, and that is where this factor comes in handy....
    Almost like working out fuel consumption on various types of makes of cars... No use driving a small car and getting the fuel consumption of a HumVee.....
    I understand Dale's point as well..... What would make sense is if you could have a microbore pipe attachment to an HPA tank to increase your reservoir capacity.... Now that would make sense, because it will give you a lot more shots in the sweet-spot region of the curve, and because of its simplicity, would be much more economical as well....

    malan
    Sign Up To Air Rifle SA Forums

  11. #11
    Sharp Shooter

    User Info Menu

    Default

    The HPA tank idea only makes sense for benchrest shooting, in the field it does not make sense.
    Sign Up To Air Rifle SA Forums

  12. #12
    Protea FT Team '06/'07/'08/'09/'10/'11/'12/'13/'14
    National FT Champ '05/'08

    User Info Menu

    Default

    why dont you invest in rifles that can shoot a lot of shots on 1 fill

    Rws 500/Daystate airwolf 500 shots per fill excellent hunting/ hft/ft rile
    Walther dominator 250 shots per fill excellent ft rifle
    Sign Up To Air Rifle SA Forums

  13. #13
    Sharp Shooter
    Doctor BAM

    User Info Menu

    Default

    Sniper
    Let's not go there.....!!!! I will pay the price of a Crosman Discovery or a BAM B-51 as a deposit for these rifles, if you are prepared to sponsor the rest.....
    It's not all about shots per fill, it is also about what is affordable to certain people.....

    malan
    Sign Up To Air Rifle SA Forums

  14. #14
    Inactive Member

    User Info Menu

    Default

    Mmmmm
    Sign Up To Air Rifle SA Forums


Similar Threads

  1. Pcp air rifle efficiency.
    By Froggy in forum Airgun Discussions
    Replies: 4
    Last Post: 10-10-18, 00:03
  2. PCP Efficiency Calculator
    By Froggy in forum Airgun Discussions
    Replies: 2
    Last Post: 24-01-13, 15:21
  3. PCP air rifle question
    By Malovent in forum Airgun Discussions
    Replies: 4
    Last Post: 16-11-11, 11:13
  4. PCP Air Fill question
    By jjmeyer in forum Airgun Discussions
    Replies: 3
    Last Post: 14-07-11, 14:14
  5. PCP filling question
    By Leadfinger in forum Airgun Discussions
    Replies: 3
    Last Post: 10-09-10, 15:37

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Friends of Air Rifle SA