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Sizeable 25m .177 pellet velocity decay test - JSB, RWS, H&N, Crosman, Pax

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

  1. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Following on from my other thread on the RWS Superfield pellet, this post contains the results for the other pellets covered in the same test.

    These were literally what I had kicking around in the pellet drawer - some are more interesting than others; there are some I'd liked to have tried but didn't have to hand.

    The full list consists of:

    Falcon Accuracy Plus 4.52
    Air Arms Express 4.52
    Daystate FT Heavy 4.52
    JSB Exact 4.52 (three different batches)
    JSB Exact 4.53
    RWS Superfield
    RWS Hobby
    RWS R10 Pistol
    RWS R10 Rifle
    RWS Supermag
    H&N Field and Target Trophy
    Bisley Magnum
    Pax Defiant

    Please note that the JSB Exact results warrant quite a bit of discussion in their own right - so I'll cover these specifically in a separate post at a later date.

    The particular sizes, weights, batch numbers are listed in the tables along with their results.


    Procedure (mainly cut and pasted from previous thread)

    All pellets were fired from a .177 HW100 in batches of five over two chronographs; one placed (as near as dammit) at the muzzle, the other a measured 25m down range. The chronys had previously been tested against each other and the marginal 0.7% variation in velocity taken into account in the processing of the results.

    From the velocity difference between the two chronys (not guns as previously stated) various bits of arguably exciting information can be calculated; including ballistic coefficient (bc) and drag coeffcient. In addition the extreme spread and standard deviation of the velocity strings over five shots at both chronographs gives an insight into consistency of pellet behaviour.

    This was a fairly quick and dirty test, but shows some interesting and fairly conclusive results IMO.



    The Pellets

    Below are images of all the pellets used in the test:

    L-R: Falcon Accuracy Plus, Air Arms Diabolo Express, Daystate FT Heavy (all made by JSB)

    [​IMG]


    L-R: JSB Exact 4.52 (batches 36000012, 46160013, 20000012), 4.53 batch no. 22560014

    [​IMG]


    L-R: RWS Hobby, RWS R10 Pistol, RWS R10 Rifle, RWS Supermag

    [​IMG]


    L-R: H&N FTT, Bisley Magnum, Crosman Premier Hollow Point, Pax Defiant

    [​IMG]

    The pellets range in age from fairly new to pretty bloody old; some (such as the H&N FTT) had oxidised slightly and this may affect performance. Similarly, it's clear that pellets do change over time and with difference batches; so these results aren't necessarily wholly indicitive of what to expect if buying the same brand now (although they should be somewhere close in most cases).


    Theory

    For those who need reminding, ballistic coefficient is a measure of how well a pellet retains velocity in flight and is a function of its mass and drag characteristics. A Higher BC projectile will lose velocity at a slower rate (i.e. will retain more velocity) than one with a lower BC.

    Conversely an object's drag coefficient is a measure of the amount of air resistance its shape generates / encouters as it passes through the air. This is defined by the object's shape only and unlike BC has nothing to do with its mass. Purely speaking, two identically shaped objects of differeing mass travelling at the same speed in the same orientation will have the same drag coefficient, but the heavier object will have a higher ballistic coefficient.


    Results

    The results for the different pellets are shown below. They're split roughly into appropriate groups (JSB, RWS and other); the Superfields are not covered since these have already been discussed in the previous post in comparison to Exacts. Apologies for the wonky formatting of the tables - it's not as easy as it looks :p


    EDIT: Results readable again thanks to @PhatMan - thanks Russ :)

    [​IMG]

    Discussion

    As previously mentioned this section will only cover an overview of the pellet sample as a whole; specific observations on the range of four different types of Exacts will be covered in a forthcoming post as there's a lot to talk about ;).

    I won't attempt to pick out every little piece of information relating to each pellet (we'd all be here all night if I did :p) however will highlight information I think is relevant. Velocity results won't be mentioned much as those relating to ballistic and drag coefficients are usually more insightful and useful.

    There are many, many more obsevations I could make on this data, but some is better left to more specific tests in future.
    - The Daystate FT Heavy retained the highest proportion of its muzzle energy at 25m (8.95ftlb or 78.2%) and gave the highest (best) ballistic coefficient of 0.028lb/in^2, while the RWS R10 Pistol only had 5.41ftlb or 47.4% of its muzzle energy remaining at 25m; correspondingly giving the lowest BC of 0.009lb/in^2.

    - The Pax Defiant gave the lowest (best) drag coefficient of 0.302 and retained 73.7% or 8.40ftlb of its muzzle energy at 25m, while the RWS R10 Pistol gave the highest Cd of 0.690; with retained muzzle energy standing at 5.41ftlb or 47.4%.

    - Despite having similar mass and shape, the 7.43gn Pax Defiant pellets showed significantly better BC (0.022lb/in^2), Cd (0.302) and energy retention (73.4% or 8.94ftlb) than the 7.33gn Falcon accuracy plus; which gave figures of 0.019lb/in^2, 0.349 and 69.94% or 7.85ftlb respectively.

    - Despite their large mass the Bisley Magnum gave a BC of only 0.020lb/in^2; a figure that correlates with their high drag coefficient of 0.476.

    - The Crosman Premier Hollow Point gave a BC of 0.019lb/in^2 and a drag coefficient of 0.374.

    - All purely-domed pellets gave BC values of between 0.019 and 0.024lb/in^2, with Cd values ranging from 0.302 to 0.387.

    - All flat-nosed pellets gave BC values of between 0.009 and 0.014lb/in^2, while Cd values ranged from 0.590 to 0.690.

    - Despite being broadly similar shapes, the drag coefficients of the R10 and Supermag pellets changes with their mass (6.99gn R10 Pistol at Cd=0.690, 8.21gn R10 Rifle at Cd=0.663 and 9.23gn Supermag at Cd=0.59) and hence the velocities they were fired at.


    Conclusion

    - The high energy retention and 0.028lb/in^2 BC of the round-nosed, 10.34gn Daystate FT Heavy compared to the low 0.009lb/in^2 value for the flat-nosed 6.99gn RWS R10 pistol pellet illustrates the significant effect that both mass and nose shape (and hence drag) have on energy retention at range.

    - The excellent energy retention and 0.302 Cd value of the 7.43gn Pax Defiant compared to 0.690 Cd of the 6.99gn offers a stark illustration of how a difference in head shape massively affects pellet drag - in this case causing flat-nosed pellet to lose velocity at nearly 2.5 times the rate of a similarly weighted, round-nosed equivalent. The drag characteristics of the Defiants are excellent, and no-doubt the result of it's apperently perfectly-hemispherical head shape.

    - The excellent BC, Cd and retention figures for the Pax Defiant compared to the Falcon Accuracy Plus again highlight the importance of head shape in reducing drag.

    - The perhaps unexpectedly low BC figure of 0.020 and high Cd value of 0.476 for the Bisley Magnum again suggests that its less-than-optimum, semi-pointed nose is responsible for creating excessive amounts of drag in flight and once-more illustrates the importance of nose shape.

    - The 0.019lb/in^2 BC figure for the Crosman Premier Hollow Point is uncharacteristically high for a hollow-point design; perhaps on account of a combination of its relatively small cavity and fairly small head radius / pronounced dome. While this in itself sounds promising, the p****d cavity edge shown in the pellet image doesn't bode well for accuracy, which is a shame.

    - The relatively consistant Cd figures for the round-nosed pellets (despite their length or waist size) again points to nose shape being the defining factor when assessing pellet drag.

    - As above, the close-grouping of the Cd values for the flat-nosed pellets supports the importance of nose shape. This is also supported by the significant difference between values for flat and round-nosed pellets.

    - The apparent correlation between drag coefficient and pellet mass in the RWS sample range (exc. the Hobby) appears to support the theory that Cd changes with velocity (or Mach no. as Miles keeps telling me ;)); implying that flat-nosed pellets generate disproportionately lower drag at lower velocities (in comparison to those tested here anyway); and that all pellets have a "preferred" velocity range within which they generate the least drag.


    What Have We Learned?

    For me the standout elements of this test are that (unsurprisingly) nose shape has a massive impact on pellet energy retention at range; with flat-nosed pellets exhibiting on average around twice the drag of their domed counterparts.

    In addition I was a little surprised by the low BC of the Bisley Magnum and the relatively high BC of the Crosman Hollow Point; both potentially being explained to some extent at least by their nose shape.

    The difference in drag characteristics with velocity for the RWS flat points (and corresponding suggestion of a relationship between Cd and velocity) will definitely lead to some testing at various velocities in future, I think :)

    Finally I'd like to say how impressed I am by the Pax Defiant. Like pretty much everyone else I've had zero success with any of Pax's offerings in the past (Prometheus, Paragon, Sn range etc) and had pretty much written them off as a product not even worth bothering with. In massive contrast the Defiants have shown excellent drag performance (the lowest of any pellet I've tested) and I look forward to testing them further for accuracy. IMO their-near hemispherical head shape is responsible for their excellent drag characteristics and while this pellet appears excellent in its own right, using the same head shape on a heavier pellet would potentially give some seriously high BC figures - around 0.030+ for a 10gn pellet by my estimation. Good work Pax :)
     
    Last edited: Sep 20, 2019
    Glockwomble, Geezer and bucketboy like this.
  2. Clubshot

    Clubshot Clubshot

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    Not forgetting that Defiants are made from Quality Lead Wire - Stamped out on Single Dies

    As Designed to be flater Shooting than Wasted Design Air Gun Pellets

    Reason that the Defiants are made in Different Head Sizes to cater for most of today's Air Rifles & Pistols


    www.defiantpellets.com

    BOB/R
     
  3. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Images updated; even though the tables are now toast hopefully some might find the conclusions of interest..
     
  4. PhatMan

    PhatMan Keyboard Hero

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    Cloverleaf,

    I did some firkling to get the data in an html file, but can't seem to load an html up :(

    In the meantime, please find enclosed pdf version of results tables.

    Have fun & a good weekend :)

    Best regards

    Russ
     

    Attached Files:

  5. PhatMan

    PhatMan Keyboard Hero

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    Hello to All,

    Have fun & a good weekend :)

    Best regards

    Russ

    [​IMG]
    [​IMG]
    [​IMG]
     
  6. rgc_swanseaARC

    rgc_swanseaARC He's not the Stig...He's the Stigs Welsh cousin

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    If you havent already, have a little dabble with H&N Sniper medium.

    Similar ish to Pax and very accurate through some of my barrels with a high BC.
     
  7. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    Nice work Russ - thanks!

    I was initially a bit confused by the additional bits on the RHS, but now see that the column spacing has gone a bit awry as some of the cells were merged.. it's all perfectly readable if you know this though and great to have the numbers back for reference :)


    I haven't, although don't doubt what you're saying considering the BC of the lights is comparable to the Exacts despite weighing over a grain less. Have you done any BC testing with them? Crudely scaling based on mass would suggest a BC of around 0.025 which would be very good :)

    I generally liked the Lights, however accuracy wasn't as good as the AA Express and I was finding the odd few with split skirts. Have you found any Mediums like this? Perhaps I just had a bad batch..
     
  8. rgc_swanseaARC

    rgc_swanseaARC He's not the Stig...He's the Stigs Welsh cousin

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    H&N quote 0.029, and 8.5gn
    Not done any BC testing only accuracy testing.
    Ive had one or two very thin skirts but not to the point of splitting.
    My results are similar, very good but for out and out accuracy they haven't beaten Jsb Express in my barrels yet.

    Happy to send you some if you want to do a bit more in depth testing than I have.
     
  9. Wewekokowe

    Wewekokowe Busy Member

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    It sucks to be restricted to sub12, a better test would have been all pellets leaving the muzzle at the same speed and see what is the performance at long range. I know it takes lot more work to do it. Tuning involved.

    But that would be a different way looking at it.

    Your experiment does not control the speed but it is what it is - limited by the energy - sort of - which is also not constant unfortunately between pellet types so still the initial conditions are not identical.

    I would want to see someone with fac doing the same experiment as the initial muzzle velocity is influencing your results too much. You need the same speed at the muzzle then you can compare.

    Then I would use the speed as parameter and repeat/chart. Let’s say a full set of data all pellets at 575fps first then 775, 900 for example. Plus another chrony at 40 with a small plexy window would add another dimension to it too

    Your experiment is still good, but it is a limited way of looking at the whole picture. In the limited sub12 environment you should have used the exact same muzzle energy then it would have been a better comparison. This experiment just shows your gun with the current tune with different pellets.
     
    Last edited: Sep 21, 2019
  10. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    I agree that in an ideal world it would have given a more complete picture to have tested each pellet over a prescribed velocity range to get an idea of how all perform with respect to velocity. However; this was not the object of the test, would have been far more time consuming and as you say potentially been hampered by legal constraints.

    That said in no way do I see this test as flawed. Conducting all tests at approximately the same muzzle energy perfectly echoes the real world and as such IMO holds more validity and relevance than testing all pellets at the same velocity. The approximate constant across different brands of ammo through the same rifle is energy, not velocity.

    Certainly, this test reflects the performance traits of my particular rifle; which in turn is broadly indicative of others of its type and to a lesser extent most 12ftlb PCPs. Tbh I see little value in taking the time to ensure the muzzle energy is the same across all pellets as this would often only be a difference of a few percent in terms of velocity, which IME would have little-to-no effect on the BC values generated.

    In addition, while it's all very commendable trying to cover all variables, in practice it's impossible to assess all factors at once / cover all bases. For example, even if testing under the regime you suggest, who's to say how the results would differ from those derived with a rifle of different barrel length, operating pressure, muzzle attachment, barrel twist rate etc...?
     

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