Does Ballistic coefficient vary from barrel to barrel?
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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Old one yes.
From what I understand BSA no longer make barrels, they are made in Spain by Gamo for them now.
Bsa
L/W
CZ
FX S/T
However the experiment was not to test accuracy so to speak.. Too many variables for that one, pellet head size v/s choke size, wind etc.. They all had room to improve and would with carefull pellet selection.
I will share more info once the new prototype .25 bench rest build is completed.
http://www.talonairgun.com/forum/viewtopic.php?f=11&t=35540
is this an old model bsa or a newer bsa barrel? i remember you saying that the older BSA barrels were much better then some of the newer ones
Order of accuracy was
Bsa
L/W
CZ
FX S/T
However the experiment was not to test accuracy so to speak.. Too many variables for that one, pellet head size v/s choke size, wind etc.. They all had room to improve and would with carefull pellet selection.
I will share more info once the new prototype .25 bench rest build is completed.
http://www.talonairgun.com/forum/viewtopic.php?f=11&t=35540
I stacked Stone tiles in a way that exposed the hole of my air chrony, so if I missed the pellet would go into Stone and not chrony
All barrels I tested were fitted to the same regulated PCP on the same day and cut to the same length (22″)
I shot over chrono’s at 50m and 100m to get very accurate figures of B.C and velocity retention.
I also shortened the barrels 1/2″ down to 18″ at a time and the figures remained very much the same.
I am not going to release all the velocity and BC variations here as last time I spoke about it I upset a few people but I will list them for you in order of performance best to worst.
BSA
CZ
Lother Walther (very close to CZ)
FX smooth twist
Something I learned very fast was the faster you push a pellet down a FX S/T the worse it got. I can only pin that on the pellet stripping of lead through the S/T section of rifling and it having an effect on twist rate and stability
I have settled on an 18″ hammer forged BSA barrel an have learned never attempt to shoot a smooth twist barrel over a chronograph at 100m again :confusedn:
Wow very interesting, i would really appreciate if you could share the data. Is the above order true for accuracy also. Though I was able to shoot 1.25″ groups at 100 yards and thought of measuring the velocity at 100 yards but still was afraid of damaging the chronograph.
I have done all these tests leading up to the selection of a barrel for my .25cal 34gr long range MOA project.
All barrels I tested were fitted to the same regulated PCP on the same day and cut to the same length (22″)
I shot over chrono’s at 50m and 100m to get very accurate figures of B.C and velocity retention.
I also shortened the barrels 1/2″ down to 18″ at a time and the figures remained very much the same.
I am not going to release all the velocity and BC variations here as last time I spoke about it I upset a few people but I will list them for you in order of performance best to worst.
BSA
CZ
Lother Walther (very close to CZ)
FX smooth twist
Something I learned very fast was the faster you push a pellet down a FX S/T the worse it got. I can only pin that on the pellet stripping of lead through the S/T section of rifling and it having an effect on twist rate and stability
I have settled on an 18″ hammer forged BSA barrel an have learned never attempt to shoot a smooth twist barrel over a chronograph at 100m again :confusedn:
I would like to see the velocity difference at 100 meters between the two barrels
I have already checked that. the wildcat scope height is 2.5″ while that of Vulcan is 2.4″, not a big difference there. I also used different values for rate of twist in strelock pro but that didn’t make any difference at the distances we shoot the PCPs. Here’s what I think is going on, A pellet gets deformed by the barrel especially by the choke at the muzzle end. I think the deformation by smooth twist barrels just makes the pellet lose more velocity. In other words CZ barrel is more efficient than smooth twist.
ask the fx guys on airgun nation how is it possible that the smoothtwist is not the higher POI out of the 2
🙂
ps. be careful they will ban you if you do that.
That’s not necessarily BC that is causing that holdover difference. Scope to bore axis so most likely the cause. The only true way to test BC is velocity difference.
barrels ? (1) Are they both made from the same material and specs ? (2) Do both barrels have the same rifling configuration ? (3)
Are both guns shooting the same pellet grain at the same foot pounds ? If not then the law of physics will always come into play
and the shooting coefficient will always be different . Just like the left foot is different from the right foot and the different
use and functions of each is critical in their designed for performance .
FROM : THE BIRDMAN
One has a 24″ smooth twist barrel while other is a 19″ cz. Yes both are shooting at almost same velocity so energy is same. My assumption is that the pellet when shot from my Wildcat looses more velocity during flight as compared to when shot from Vulcan. I think smooth twist barrel has less rate of twist as compared to cz. The cz barrel is shooting the pellet more efficiently.
As far as coefficient difference between both guns go , both are made by a different maker . So , what are the differences in their
barrels ? (1) Are they both made from the same material and specs ? (2) Do both barrels have the same rifling configuration ? (3)
Are both guns shooting the same pellet grain at the same foot pounds ? If not then the law of physics will always come into play
and the shooting coefficient will always be different . Just like the left foot is different from the right foot and the different
use and functions of each is critical in their designed for performance .
FROM : THE BIRDMAN
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A friend of mine has recently got an Impact. We have been trying different settings but it was not that accurate. Tried velocities from 850 to 930fps but result wasn’t good. Then we cranked the power up and finally got the 25 cal barrel shooting groups of .4″ at 50 yards at 950 fps with jsb kings. Seems every barrel behaves different.