SMH77 heres some real world wind drift comparisons:
JSB Kings JSB King Heavies MK2
distance: 100 yds 100 yds
velocity: 868 fps 868 fps
5 MPH 90 degree wind: 6.5" 5.6"
Drop in inches: 16.4" 15.0"
So .9 inches at 100 yds. Thats a very small difference since both require significant hold off for just a 5 mph wind at 100 yds. If you decrease the distance to 50 yds theres only a .2 difference in wind drift using the same wind as the above example. Pellets just dont "buck the wind" like high speed vld bullets in firearms do. They also have a very small difference in drop but both have a huge amount of drop at 100 yds.
As far as the BC being the reason the pellet is less accurate you are confusing whats causing the decreased accuracy. The fouled barrel is the culprit to the accuracy loss. Yes the BC is lower because the velocity is lower. Velocity and BC go hand in hand but the BC number has no effect on accuracy. If BC had a direct impact on accuracy how can a .177 shooting an 8 gr. pellet be just as accurate or even more accurate than a .25 shooting a 25 gr. pellet? The .25 is going to have a much higher BC than the .17 yet there are plenty of .177 pellet rifles that are just as accurate as a .25.
The BC does not guarantee the accuracy potential it only guarantees it will retain velocity better and drift less in the wind and even thats only true if comparing apples to apples. Projectiles with lower BC numbers can and do outperform projectiles with higher BC number with less drop and wind drift if their velocity is faster than the higher BC projectile.
Pellets BC are so low that wind drift doesnt even come into play if its the same caliber for most scenarios. To go one step further here is another example of accuracy and different speeds. My S510 was tuned for 30 fpe with 18 gr. JSB. It was very accurate with that tune and it is regulated. After awhile I decided to de tune it for more shots and set the reg for a 15 fpe tune. After resetting the reg and getting my 15 fpe with the 18 gr. JSB its even more accurate than it was at 30 fpe with the same pellet. Again if the BC was a factor for the accuracy potential or lack of, how can you explain these two examples of the same accuracy or better with lower BC numbers? The only difference from my examples and yours is that my barrels were clean. So clean barrels with lower BC numbers performed as well or better than the same clean barrels with higher BC numbers and that happens everyday in the airgun world.
Just to clarify a little I am talking about comparing strictly the BC as an accuracy factor. So when I say higher BC does not increase accuracy I am talking about if you shoot lower BC pellets against higher BC pellets without any outside factors like wind. If you compared the lower BC to the higher BC using just BC numbers there will be plenty of lower BC pellets matching or outperforming the higher BC pellet in accuracy. Earlier I said the higher BC will help the shooter be more consistent/accurate in windy conditions because there will be less drift so less error to account for. I believe this to be true but very limited due to the small advantage in wind drift when comparing apples to apples. So in reality the higher BC pellet isnt more inherently accurate than the lower BC pellet. Its easily proven by shooting on an indoor range where no outside factors effect the pellet. That way its a pure test of BC against BC.
I think we are actually more in tune than may be coming across. I agree with most of what you say in your post here and have examples to back up some of it.
First, the easier stuff: I wholeheartedly agree that selecting a pellet type based on having a higher BC does not indicate it will shoot accurately in your gun. Easy example for me to reconcile: Rat Sniper slugs have signficantly higher BC's compared to the JSB heavy pellets, but the JSB pellets outshoot them handily when it comes to accurate groupings at even just 50 yards. No comparison-JSB's with the lower BC's (see the chart below). Totally on the same page as you on this point.
My other two comments are maybe more 'subtleties' than they are disagreement: [first chart and paragraph] for me, a 0.9" drift difference (almost 1 MOA) is pretty signficant at 100 yards-that shows up as a more notable 'flier' that definitely ruins a group 'worse' with the lighter BC pellet vs. the heavier pellet. But that can be argued, so I'll just leave the comment with 'my opinion' is that 0.9" less drift is a pretty significant factor. Just as a reference (from other posts) here's how the BC's of different pellets show up through the same setup (same barrel, powerplant settings, etc)-but the velocities were not (and could not) be adjusted to match each other, so that's a limitation of the comparison. Here's the link to the thread if you want to see the groupings for each pellet as well. If not, here's the BC comparison chart for two different guns, under the same testing constraints (but on different days for the FX test vs. the RAW test):
FX Wildcat Mk II Results: RAW HM1000X, polygon barrel results: (shot on different days, and environmental conditions - so don't compare across the FX and RAW charts).
My point with these charts is the difference between the lite and heavy JSB pellets is very significant - but there is also the smaller velocity component I was unable to factor out to keep the same gun, same environmental comparisons fixed.
Lastly, and this, I believe, is the whole point in my thread originally (it's gotten a bit off topic, but still very useful and interesting): you were saying that the 'fouling' is what is causing the loss of accuracy, independent of whatever is going on with BC and velocity in a dirty barrel. I am simply stating that I think the data may actually suggest that the 'fouling' is showing up IN the data as an effect on the BC and (as a result) velocities. That's really my whole point and suspicion in what is showing up clearly in the data. I hadn't intended to open up a discussion about substituting a higher BC rather than testing a pellet to barrel match for accuracy (while I would tend to try the higher BC pellets first-in hopes they shoot accurately, ultimately I'll pass on them for a better accuracy pellet as that's whats most important in the end anyway (to me)). Your second paragaph (
As far as the BC being the reason the pellet is less accurate you are confusing whats causing the decreased accuracy. The fouled barrel is the culprit to the accuracy loss. Yes the BC is lower because the velocity is lower. Velocity and BC go hand in hand but the BC number has no effect on accuracy.) is what I'm referring to with this statement. I'm simply saying this: I think the 'fouling' may actually be something you can 'see' in the velocity / BC data as I've demonstrated with the data posted at the start of this thread. I wholeheartedly agree that fouling is what is causing the loss of accuracy and indicates its time to clean the barrel.
'Velocity vs. BC' is a whole other can of worms that others have tested and posted about. There seems to be some optimal velocities to shoot pellets with given setups to get the highest BC - which doesn't necessarily coincide with the speed that will give you best accuracy results. People like Yrrah and others (Yellow forum) have tested and posted a lot about this topic.
Anyway, in the end, I just wanted to say that I don't think what you're saying is at all at odds with what I'm saying. I'm just suggesting the link between fouling and 'measurable data' may actually be present and somehow may be linked rather than repeatably coincidental. Does that make sense?
Sean
Tell me im wrong.
