Heavy and light JSB .25 cal pellets comparative ballistic drag coefficients.

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Yrrah

Yrrah

Member
Apr 1, 2015
462
86
NSW, Australia
I like to know the reality and there is nothing beats practical data collection in the field to help - will always be so I guess.
Here are two representative shots tracked to 75 yards Heavy, and to 95 yards Light, exposing their naked all: I tracked ten shot strings but as yet have to find my way through getting averages from masses of data points. I just chose shots that reflected the average speed patterns.


All comments welcome. ... Best regards, HarryYrrah.
 
YrrahThe Heavy 34 gr Kings' Ballistic coefficient is running around 0.05 to 0.055 from the FX with BSA barrel.
For those who previously asked; the ST barrel on the same rifle is giving a BC of around 0.0376 with the 34 gr Heavy King..
The lighter 25.4 gr King is averaging 0.035 to 0.036 from the BSA barrel. I didn't run it through the ST.
Regards, Harry.


Noticeably, again, pellets from the FX barrel are registering a lower BC than from the BSA barrel.

Thanks, good stuff.

Click to expand...
 
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Yet to test that Ben. I have really only now got the instrument that allows for relatively easy set up and data collection. Previously it has been a laborious task shuffling one or two chronographs to different ranges and then aligning it all and getting readings either walking to and fro' or having someone else, protected, out there to record the data. The chronograph hardware has to be protected from pellet hits usually with a piece of angle iron. The labradar is solving all that, at least to reasonable distances.
I have a lot of stuff to research of interest to me; I am not generally in the business of looking to downplay one make of rifle etc against another. We need to celebrate the tremendous efforts that individuals have put and are putting into making these wonderful rifles. It is a golden age. ...
What can pull it apart is the venture capitalists looking to buy up and then strip the quality manufacturers.
Bedtime in OZ, Kind regards. Harry.
 
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Hello Harry,

When I run your labradar numbers through chairgun and adjust for your altitude I get bc numbers that are a bit lower. Edit: just noticed you must have used the G1 drag function.

0.0475 for the King heavy out to 75 yards with a muzzle velocity of 781 fps

0.032 for the normal Kings out to 75 yards with a MV of 899 fps

Conditions: 13 C temp. 26.31 Hg atm pressure. 58% humidity. GA diabolo drag function in chairgun.

regards,

Robin
 
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Robin, I don't know why you are getting those figures.
When I put the data in (GA) ; Ambient conditions as you have them, then the start and finish velocities to the BC calculator: 781/662 at 75 yd; and 899/688 respectively and accept the results; .0505 and .0333 respectively those come up on the main page. Then if I caress the BC box with the cursor on the main page, a little drop down box tells me the BCs at the entered environmental conditions are 0.0561 and 0.037 respectively for the Heavy and light Kings.. ..... Not sure why we get something different. Thanks for your interest, Kind regards, Harry.
 
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