Ballistic coefficient, does it vary from barrel to barrel?

Those are very different barrels, so naturally you will have very different results.

i thought it varied by speed, i found a formula and calculated it from speed at to different distance's.

Yes but speed from two different ranges right? It calculates how much speed is lost at a set distance, different barrel wil peform different

"hsnmz"I have a Wildcat and a Vulcan both 25 cal. Both are working at almost identical velocities. I use a ballistic coefficient of 0.036 in strelock pro which is the default value for jsb kings. At 100 yards strelock suggests a holdover of 3.5 mildots. my Wildcat hits exactly at 3.5 mildots but my Vulcan hits half mildot higher i.e. at 3rd mildot. I had to correct the bc to 0.048 in strelock to get the holdover corrected for Vulcan.
So the question does ballistic coefficient vary from barrel to barrel?

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Did you take the height between the center of the scope and the center of the barrel into account? This also makes a small difference. I don't know if this makes a difference of 0.5 mildot.

And BC value will indeed vary with barrels.

I thought BC was only based on the shape of the projectile?, I assume if the two barrles are adding there own unique rifleing groves to the pellet it would change the shape and therefore change the BC?

Is this line of thought ccorrect?

hsnmz Back your crono out to around 20yds. 
You will likely see the Vulcan is faster and the further you go the bigger the difference.
Its spin rate whether faster or slower is giving the pellet a higher BC.

That's why Eric is saying measure at two different distances.

If you go to the AoA website there calculator requires two speed imputs at two different range's

from what i understand. the rifling in the barrel can deform pellet and change then BC slightly. 

mysource:

Polygonal and Rifled Barrels compared for BC and Velocity

j.le

Ballistic Coefficient (BC) is basically a measure of how streamlined a bullet is; that is, how well it cuts through the air. Mathematically, it is the ratio of a bullet's sectional density to its coefficient of form. Ballistic Coefficient is essentially a measure of air drag. The higher the number the less drag, and the more efficiently the bullet cuts through the air. So for purposes of flying through the air efficiently, the bigger the BC number the better.


BC is what determines trajectory and wind drift, other factors (velocity among them) being equal. BC changes with the shape of the bullet and the speed at which the bullet is traveling, while sectional density does not. Spitzer, which means pointed, is a more efficient shape than a round nose or a flat point. At the other end of the bullet, a boat tail (or tapered heel) reduces drag compared to a flat base. Both increase the BC of a bullet.

I googled it lol

"hsnmz"

"broekzwans"
Did you take the height between the center of the scope and the center of the barrel into account? This also makes a small difference. I don't know if this makes a difference of 0.5 mildot.

And BC value will indeed vary with barrels.

Click to expand...

Yes I have carefully measured that. the scope height on wildcat is 2.5 inches and thatvon Vulcan is 2.4 inches, not a big difference. I think it's all due to the barrels. Seems the CZ barrel is shooting the pellet more efficiently.

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From memory I believe that the Chairgun scope height is measured from scope LOS to barrel LOS as measured at the muzzle.

“Scope height” is actually the wrong name for this parameter. The actual parameter needed is the difference between the line of sight and the center of the barrel at the MUZZLE.