Originally Posted by CarmatechEng
UV Halo as with others in this group have done substantial testing in relation to fs rounds. I remember reading a writeup by UV regarding ballistics of the rounds. I believe that he was able to estimate BC based on round drop at a specific range. Up till recently I have been using these numbers to calculate ballistics. We recently purchased two light sensitive chronographs. We set these two chronographs 100 feet apart and shot the SAR12 through both with the same shot. What we found was not suprising, but it did give us scientific data to proceed with. We found that the difference in velocity of a FS round at 100 feet was around 25 fps when comparing a rifled barrel and a smoothbore barrel. Obvious was the fact that the rifled barrel was more efficient. Both barrels were within .002 inch on bore diameter, thus we can neglect bore issues. Both tests were set to which the projectile left the barrel at 300 fps, and as advertised the shots didn't deviate more than plus minus 1 over testing. Regulator adjustments were necessary when we switched between the 20inch rifled barrel and the 16 inch CP barrel. Obviously both barrel manufacturers are known for quality.
This test validates the theory of prespinning the projectile makes for a more efficient flight. Finally we have started to evaluate which ballistic model to be using for the FS projectile, and it seems that the best bc model is the GA as the cross section of air gun pellets are very similar. We also did this test with paintballs and found that the BC for a paintball is .011 using the GS model
David- actually my ballistic coefficient is derived from a 19 shot test sample of rounds fired over two chrono's 100ft apart by Punkworks (they did the test before consulting me,l and unfortunately the thread containing the majority of the information got corrupted and lost).
Also, you don't need nor benefit from having the chrono's so far apart. You just need to be sure the difference in velocity is outside the error of the chrono's being used. Over a longer distance, I believe due to the arc required, gravity may start to be an influence (how much? I'm not sure).
That's cool to hear about the GA/GS Models- That's a new feature in Chairgun 4 that wasn't around when I was running my numbers. However, I'd like to know why you think the GA model is better for FS rounds. I ask because the Diabolo pellet it is based on is very 'waisted' with a relatively flatter nose than an FS round.
My last question for now: I understand if the answer will be "No" as I understand you're running a business and likely doing all of your testing on the 'company's dime'. But, I must ask anyways:
Can you release the raw data and testing parameters (indoors/outdoors, elevation, for community analysis? Myself, and many others would find this this information beneficial and much more valuable than the conclusion.
Originally Posted by tangus999
What your determined ballistic coefficient for FS?
I found it to be .0162 at 1000ft altitude, 70deg F when fired from a smoothbore barrel.