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Thread: Ballistics

  1. #1
    Marksman

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    Default Ballistics

    Hi everyone

    If all goes well I will at last leave for home tomorrow and get to hold my new aquired rifle/hobby/postponing of buying a new car with probably another year.

    I've read up alot on zeroing a scope and would just like to ask if I understand the following correctly. According to chair gun shooting the Jsb 18.13g with the condor at approximately 950ft/s the rifle should zero at 20 yards and far zero at 40 yards with a flat spread inbetween of around 0.6cm POI variable inbetween. If I move the far zero to 50 yards the spread seems to move to up to 1.9cm variable at the POI.

    I understand how the projectile comes through the scope twice due to the drop in the projectile, the scope in theory pointing down and the rifle up, but can a far zero of 10 yards more make such a big difference with a BC of 0.027?

    Would I be correct in saying that for the speed, weight of projectile and so forth my zero distances of 20-40 yards would be the best for this setup? If set up like that it would mean a 1mil dot hold over at 60 yards. Doubt I'll be shooting that far anytime soon.

    I like numbers and love reading about projectiles moving through the air and how different forces affect them, that's why I became a pilot by profession. But this airgunning is still foreign to me and like everything in life I like to understand first and then apply.

    Thanks alot
    Wynand

    (I also found R10000 of savings that should probably be applied towards another rifle. Might bug everyone again for some advice on a springer. )
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  2. #2
    Marksman

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    Very interesting, I will be following this post. If you ever want to sell your Condor let me know
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  3. #3
    REP: WS Airguns

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    Wynand still has to shoot that nice rifle. It was on the forum, and nobody but Wynand reacted to the for sale post.
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  4. #4
    Marksman

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    I have aquired quite a few pellets while in Jhb and have to ask you a few questions about springers. Hierdie goed maak my baie deurmekaar, maar van ek in jhb is moes ek al drie keer data koop agv van reviews, ballistics en verskillende gewere oplees.

    Ek sien baie uit om jou te ontmoet en bietjie vrae te vra. Meskien kan ek jou eendag die bos wys daar in Botswana.
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  5. #5
    Marksman

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    Quote Originally Posted by Judd Sherrin View Post
    Very interesting, I will be following this post. If you ever want to sell your Condor let me know

    If I have to be very honest I've only shot other people's pcp's. I doubt the condor will be for sale soon. If you're close to jhb I'll be in Centurion from the 17th of February if you would like to feel the rifle and shoot it.

    My dad will also be up in jhb so planning on burning some powder and doing some quality father son time just chilling and doing some friendly target shooting with the Steyr Mannlicher. (As the only son I know where that rifle is going)

    Regards
    Wynand
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  6. #6
    Marksman

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    Hi Lostinbots,

    I share your appreciation of numbers, and have gone down the road your are about to embark on.

    This airgun thing is a little bit of a puzzle sometimes. BC is tied to many factors, one of those factors is pellet speed, another is your barrel, another is the pulse of air behind the pellet, yet another is the gush of air passing the pellet as it exits the crown. Scope height is a major factor to your zero range, I shoot at 100m so elected for a single/precision zero at 29 meters, so your 20y to 40y range is in the ball park. Doing a two point zero also requires hold unders, or negative clicks at some ranges, as the trajectory is really loopy I feel that doing a single point zero provides more room on the scope when using adjustable scope rings, it also zeros you at the top of the trajectory arc so all ranges are hold over or positive clicks.

    I think that your speed is a little high for 18.1, am assuming they are JSB, maybe shoot the gun at different speeds just for groups, you will definitely find a speed that groups better, this speed then should be used to determine your zero distance. I found that in my 5.5mm CZ barrel that a speed of 870FPS was amazing, but noted also that at 100M I was hitting higher than chairgun said I should.

    This brings me to Strelok, available on iphony and hemorrhoid, this program allowed me to calculate real world BC based on pellet drop, and to extrapolate those results to a delta value for either speed or BC, great program, if you are willing to gather and input valid data for your specific rifle, pellet and conditions, do you have a chrony? If you love numbers, please get a chrony.

    I discovered that a change of speed from 900 FPS to 870 FPS actually improved my BC from a published .033 to .035. This small change is significant as at 100m you want the best BC for accuracy, who cares what speed that is achieved at (as long as its not below 840 FPS)?

    Don't make the mistake that I made and rely on published data, don't listen to what I, or others run their guns at, don't even listen to other Airforce owners. Do your own testing and use a program like Strelok to provide you with both firing solutions and directional vectors, you will love the results, as they will be yours.

    Ranging a target at say 82.5 meters and inputting the data into Strelok provides you with a click value for your scope that will place the pellet on the cross-hairs , its an amazing feeling seeing all your hard work result in precision shot placement.
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  7. #7
    REP: WS Airguns

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    Great info RiazP, I will be taking the chrony with to the range when Wynand plays with the power settings and and pellet weights.
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  8. #8
    Marksman

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    Thank you very much for your valuable info. I shot the rifle for the first time yesterday leaving everything as I received it. Only shot at 25m and it's dead on target. Could only fI'll to 2000psi so wil have to go and check tomorrow who can fill up my scuba tank and do the external inspection.

    I was thinking of buying a springer with some cash taken from the "I want a hilux savings account" but have come to the conclusion that that money would be better invested for a chrono and a compressor to fill my scuba tank (Living in the middle of nowhere has its disadvantages).

    I will go out and shoot with Wimpie over the duration of the next two weeks so he can teach me a few basics (I had to phone him yesterday as it seems I have a fear of connecting two high pressure bottles) and then when back home I will start tinkering a bit.

    Also think I would take Scout Snipers advice and Polish the valve stem and put a small O-ring under the top hat. Watched some youtube video's and it seems easy enough. Once I'm fully set up I'm sure I will have some more questions. Also got myself a dedicated note book that will stay in my rifle case. At the moment the power wheel is set on 3-7. And the rifle exceeded my wildest expectations.

    Just want to thank Wimpie who always has time to answer my questions, and having the faith to wait when I had to send the money from Botswana to South Africa. It's not easy to trust strangers these days.

    Regards
    Wynand
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