This thread is VERY LONG so sit comfortably and bring your Pop-Corn....
This topic originated after a member from this forum assured me that given the fact that the BC for his 10.3 gr, JSB's (.177) were higher than the BC's published for the same mass (weigh) slugs, he believed that the 10.3 gr, pellet would OUTPERFORM those slugs of similar mass...
By outperforming we discussed: Trajectory, precision and wind drift...He also seemed to believe that the higher BC implied higher precision...
This is my response and I kindly ask all of the Internet "Know it all" and bullies to restrain from answering before researching the topic, this thread is not about what anyone believes it is, this topic is about facts proven at an aerospace lab and I will try to explain them in very simple terms omitting complexities.
Scientific Fact NOT subject to discussion: You will never outperform a slug with a pellet of the same mass/caliber unless of course, the slug has a wad cutter head shape or similar high drag shape....The slugs we are talking about have an ogive head form 2-S and can have different construction: Hollow point, solid, hollow body with a smaller hollow point...Any of those configurations will fall into the G1 model (BC shape) and all of these configurations BY PRINCIPLE OF AERODYNAMICS WILL OUTPERFORM a pellet of the same mass that by definition falls into the GA model...A slug will always have better trajectory and accuracy and less wind drift unless of course, there is a flaw in the design.
Don't ever confuse BALLISTIC COEFFICIENTS with PRECISION....Most shooters believe that the higher the BC the more precise the pellet will be....THIS IS JUST NOT THE CASE!...Memorize this because I've seen innumerable videos and posts from the so called "Experts" suggesting to use the highest BC and this is confusing and wrong in this sense.
Keep in mind that the G1 model comes from the late 1800's and that the 1 number means that it was a projectile with a mass of 1 pound and 1 inch in diameter... This projectile by no means if the epitome of precision nor accuracy...It has a value of 1 so any pellet/bullet with that shape is only compared to the performance of that particular G1 Projectile and this has no correlation with its precision. People should look for high BC projectiles for a better trajectory and wind drift and test-compare lower and higher BC's when looking for precision, you will find many bullets, pellets and slugs with lower BC's that are much more precise than the ones with higher BC's.
I noticed that you gave me the BC's for the 10.3 gr. pellets comparing them to the BC's published for Nielsen and other slugs of similar mass...Since the BC published for the 10.3'is higher than the one published for the slugs you used this argument to support your theory of why in your opinion, a 10.3 gr. pellet will outperform Nielsen and other slugs with similar mass (weight) around 10.3 grains...
Let me explain your confusion...Pay attention to what I am going to say and do some research if necessary so you learn something: Conventional pellets (Diabolo shaped) publish their BC's based on the GA model which considers the shape of the head of the pellet, slugs that have 1/2, 3/4, 1 or 2-S Ogive shapes which is the case for the slugs we are talking about, DO NOT resemble the head of a pellet and their BC's are based on the G1 model which is calculated for short flat-bottomed bullets/slugs...
The difference in performance in between a G1 and a GA model is enormous and this is why the numbers (BC's) are not comparable!
If you were to convert the GA equivalent numbers to G1 the BC's would be some 30-40% lower (I have a mathematical model that does this at my office in Seattle and don't have it handy here in MT, I am speaking in general terms)...The very same will happen if you compare BC's from G1 and G7 which are the boat tail flat based elongated 2-S shaped projectiles (these have very low drag). I believe we still don't have slugs with boat tails for airguns, but I know that there are some people working on them.
Another confusion you have is that a higher BC will outperform a lesser BC in a pellet of the same mass...This concept is at error in the sense that since diabolo shaped pellets are stabilized by drag and rotation, the initial velocity has much to say about the BC changes during the flight of the projectile...Let me give you an example plugging in some imaginary numbers as I don't have any of my records/statistics available: Let's suppose that you shoot your 10.3 gr, pellet at 700 fps....You will then have an initial muzzle BC that will change over time (flight of the projectile). Since you will shooting the same gun in both instances, we will not talk about twist ratios, rifling profiles, etc..affecting the initial BC and will only consider the velocity factor...
Now let's shoot that very same pellet at 1,000 fps...Which pellet will have the higher BC? ...You are going to respond that the one shot at 1000 fps and that this is correct, BUT ( a big but) this is the BC at the muzzle and NOT the BC at all distances...If we later compare the BC's from the pellet shot at 700 fps with the pellet shot at 1000 fps. at a distance of let's say 75-100 yards or even closer, you will be surprised to find out hat the BC for the pellet shot at slower velocity has a higher BC!. This means that the slower pellet will OUTPERFORM the faster pellet at those distances.
You will ask me but WHY?...The reason is that a diabolo shaped pellet is stabilized by drag and rotation, when the projectile leaves the barrel the spinning is doing most of the stabilization, but then we have the fact that velocity drops close to exponentially vs. the rotation of the pellet and the resultant is more drag placed on the pellet that lowers the BC very quickly up to the point where drag takes over spinning...This means that from here on the pellet will be stabilized more by drag than by rotation....The higher the MV the more drag that lowers the BC faster at further distances.
When the pellet leaves the barrel, the velocity combined by the rotation place the head of the pellet (CG or center of gravity) in the direction of the line of departure (center of the bore), drag from the waist and skirt of the pellet fight that position all the way while spin has the command...Then velocity drops at a close to exponential rate and this helps the drag, mainly coming from the waist/skirt fighting the spin for controlling the direction of the CG of the pellet...The spin wants line of departure while their is enough velocity and drag wants to follow the gravity (TRAJECTORY) and the angle between line of departure and trajectory is the angle of attack..This angle of attack also applies to bullets (line of departure vs. trajectory)
After some time at the exact moment when drag takes over spin, the pellet receives a destabilizing "Shock" that tends to flip the CG (center of gravity of the pellet around the head)...This shock is as explained, generated by the SPIN inducing a force to the CG (pulling it up) to follow the line of departure and on the other side DRAG pulling the CG down to follow the trajectory (gravity/time)...Visualize this as a fight of SPIN pulling up to line of departure and DRAG pulling down to comply with gravity (trajectory)....DRAG for those who don't know how it applies to pellets, it is similar to the flight of a badminton shuttlecock.
The greater the angle of attack the greater the shock....Understand what I am saying
Note: I am looking forward to seeing the posts and videos of the so called "Forum Experts" explaining this fight and taking the credit for it.
To summarize: When the switch from rotation to drag happens, the pellet receives a shock that diminishes/DESTROYS its aerodynamic flight...So we have 3 vectors: One pushing from behind (velocity) another pulling up (Spin) and a third one pulling down (Drag). As said, this shock destabilizes the movement (flight) of the pellet and this is what causes what shooters call: "Cork screw spinning"...
By comparison: You will "NEVER" see a slug with precesion or nutation movements unless the projectile is defective or was constructed without a good balance between CG (center of gravity) and CP (center of pressure).
Pellets shot from a SMOOTH BARREL (No Rifling) will NOT have precession nor nutation...There is no angle of attack nor spin to "fight", the pellet stabilizes 100% by drag and follows the trajectory until it hits the target or falls into the ground...Let's not talk about trajectory and wind drift coming out of a smooth bore.
Bullets do have both of these movements because the distance between CP and CG is long and this factor combined with the shock induces tumbling that progresses to precession and nutation...Wind has also a big influence at tbis point in time when the shock happens.
We call this destabilization point (shock) the "Aerodynamic Point of Inflection" (API)
The cork screw effect over a straight line is technically called PRECESSION and the cork screw effect circling 360 degrees is called NUTATION.
A Tip: Shooters who have issues with their pellets shooting accurately let's say up to 110 yards but complaining about losing the precision at 120 yards give or take and at farther distances, this is what is happening to your pellets....How to resolve this issue you ask?
Estimate the BC at the distance where the pellet loses control (Use any Dopler chrony) and move this BC you found slightly ahead of max distance you will be shooting...Also calculate the pellet rotation at that distance so you known when is it that drag takes over spin. In other words: The destabilizing BC at the Aerodynamic Point Of Inflection (API) moved to farther distances slightly ahead from the max distances you will be shooting will determine the distance for the new API, AS SIMPLE AS THAT!
The other only alternative which is not my favorite, is to use a very low TR barrel and shoot at a higher velocity so the spin is not that high (less drift and turbulence)...The inconvenience is that this alternative would usually generate more drag derived from the lack of spin and it will come with its draw backs: Drift among them and less precision at longer distances; the BC at those farther distances would be lower given the fact that the projectile has been stabilized by drag for a longer period of time...
I will NOT be responding to bullies or to stupid questions/contradictions coming from "know it all wannabees" but will gladly answer any doubts.
Stay safe and hang in there, we will all come out of this crisis much better persons valuating what is important in life.
Please all receive my best regards,
AZ
This topic originated after a member from this forum assured me that given the fact that the BC for his 10.3 gr, JSB's (.177) were higher than the BC's published for the same mass (weigh) slugs, he believed that the 10.3 gr, pellet would OUTPERFORM those slugs of similar mass...
By outperforming we discussed: Trajectory, precision and wind drift...He also seemed to believe that the higher BC implied higher precision...
This is my response and I kindly ask all of the Internet "Know it all" and bullies to restrain from answering before researching the topic, this thread is not about what anyone believes it is, this topic is about facts proven at an aerospace lab and I will try to explain them in very simple terms omitting complexities.
Scientific Fact NOT subject to discussion: You will never outperform a slug with a pellet of the same mass/caliber unless of course, the slug has a wad cutter head shape or similar high drag shape....The slugs we are talking about have an ogive head form 2-S and can have different construction: Hollow point, solid, hollow body with a smaller hollow point...Any of those configurations will fall into the G1 model (BC shape) and all of these configurations BY PRINCIPLE OF AERODYNAMICS WILL OUTPERFORM a pellet of the same mass that by definition falls into the GA model...A slug will always have better trajectory and accuracy and less wind drift unless of course, there is a flaw in the design.
Don't ever confuse BALLISTIC COEFFICIENTS with PRECISION....Most shooters believe that the higher the BC the more precise the pellet will be....THIS IS JUST NOT THE CASE!...Memorize this because I've seen innumerable videos and posts from the so called "Experts" suggesting to use the highest BC and this is confusing and wrong in this sense.
Keep in mind that the G1 model comes from the late 1800's and that the 1 number means that it was a projectile with a mass of 1 pound and 1 inch in diameter... This projectile by no means if the epitome of precision nor accuracy...It has a value of 1 so any pellet/bullet with that shape is only compared to the performance of that particular G1 Projectile and this has no correlation with its precision. People should look for high BC projectiles for a better trajectory and wind drift and test-compare lower and higher BC's when looking for precision, you will find many bullets, pellets and slugs with lower BC's that are much more precise than the ones with higher BC's.
I noticed that you gave me the BC's for the 10.3 gr. pellets comparing them to the BC's published for Nielsen and other slugs of similar mass...Since the BC published for the 10.3'is higher than the one published for the slugs you used this argument to support your theory of why in your opinion, a 10.3 gr. pellet will outperform Nielsen and other slugs with similar mass (weight) around 10.3 grains...
Let me explain your confusion...Pay attention to what I am going to say and do some research if necessary so you learn something: Conventional pellets (Diabolo shaped) publish their BC's based on the GA model which considers the shape of the head of the pellet, slugs that have 1/2, 3/4, 1 or 2-S Ogive shapes which is the case for the slugs we are talking about, DO NOT resemble the head of a pellet and their BC's are based on the G1 model which is calculated for short flat-bottomed bullets/slugs...
The difference in performance in between a G1 and a GA model is enormous and this is why the numbers (BC's) are not comparable!
If you were to convert the GA equivalent numbers to G1 the BC's would be some 30-40% lower (I have a mathematical model that does this at my office in Seattle and don't have it handy here in MT, I am speaking in general terms)...The very same will happen if you compare BC's from G1 and G7 which are the boat tail flat based elongated 2-S shaped projectiles (these have very low drag). I believe we still don't have slugs with boat tails for airguns, but I know that there are some people working on them.
Another confusion you have is that a higher BC will outperform a lesser BC in a pellet of the same mass...This concept is at error in the sense that since diabolo shaped pellets are stabilized by drag and rotation, the initial velocity has much to say about the BC changes during the flight of the projectile...Let me give you an example plugging in some imaginary numbers as I don't have any of my records/statistics available: Let's suppose that you shoot your 10.3 gr, pellet at 700 fps....You will then have an initial muzzle BC that will change over time (flight of the projectile). Since you will shooting the same gun in both instances, we will not talk about twist ratios, rifling profiles, etc..affecting the initial BC and will only consider the velocity factor...
Now let's shoot that very same pellet at 1,000 fps...Which pellet will have the higher BC? ...You are going to respond that the one shot at 1000 fps and that this is correct, BUT ( a big but) this is the BC at the muzzle and NOT the BC at all distances...If we later compare the BC's from the pellet shot at 700 fps with the pellet shot at 1000 fps. at a distance of let's say 75-100 yards or even closer, you will be surprised to find out hat the BC for the pellet shot at slower velocity has a higher BC!. This means that the slower pellet will OUTPERFORM the faster pellet at those distances.
You will ask me but WHY?...The reason is that a diabolo shaped pellet is stabilized by drag and rotation, when the projectile leaves the barrel the spinning is doing most of the stabilization, but then we have the fact that velocity drops close to exponentially vs. the rotation of the pellet and the resultant is more drag placed on the pellet that lowers the BC very quickly up to the point where drag takes over spinning...This means that from here on the pellet will be stabilized more by drag than by rotation....The higher the MV the more drag that lowers the BC faster at further distances.
When the pellet leaves the barrel, the velocity combined by the rotation place the head of the pellet (CG or center of gravity) in the direction of the line of departure (center of the bore), drag from the waist and skirt of the pellet fight that position all the way while spin has the command...Then velocity drops at a close to exponential rate and this helps the drag, mainly coming from the waist/skirt fighting the spin for controlling the direction of the CG of the pellet...The spin wants line of departure while their is enough velocity and drag wants to follow the gravity (TRAJECTORY) and the angle between line of departure and trajectory is the angle of attack..This angle of attack also applies to bullets (line of departure vs. trajectory)
After some time at the exact moment when drag takes over spin, the pellet receives a destabilizing "Shock" that tends to flip the CG (center of gravity of the pellet around the head)...This shock is as explained, generated by the SPIN inducing a force to the CG (pulling it up) to follow the line of departure and on the other side DRAG pulling the CG down to follow the trajectory (gravity/time)...Visualize this as a fight of SPIN pulling up to line of departure and DRAG pulling down to comply with gravity (trajectory)....DRAG for those who don't know how it applies to pellets, it is similar to the flight of a badminton shuttlecock.
The greater the angle of attack the greater the shock....Understand what I am saying
Note: I am looking forward to seeing the posts and videos of the so called "Forum Experts" explaining this fight and taking the credit for it.
To summarize: When the switch from rotation to drag happens, the pellet receives a shock that diminishes/DESTROYS its aerodynamic flight...So we have 3 vectors: One pushing from behind (velocity) another pulling up (Spin) and a third one pulling down (Drag). As said, this shock destabilizes the movement (flight) of the pellet and this is what causes what shooters call: "Cork screw spinning"...
By comparison: You will "NEVER" see a slug with precesion or nutation movements unless the projectile is defective or was constructed without a good balance between CG (center of gravity) and CP (center of pressure).
Pellets shot from a SMOOTH BARREL (No Rifling) will NOT have precession nor nutation...There is no angle of attack nor spin to "fight", the pellet stabilizes 100% by drag and follows the trajectory until it hits the target or falls into the ground...Let's not talk about trajectory and wind drift coming out of a smooth bore.
Bullets do have both of these movements because the distance between CP and CG is long and this factor combined with the shock induces tumbling that progresses to precession and nutation...Wind has also a big influence at tbis point in time when the shock happens.
We call this destabilization point (shock) the "Aerodynamic Point of Inflection" (API)
The cork screw effect over a straight line is technically called PRECESSION and the cork screw effect circling 360 degrees is called NUTATION.
A Tip: Shooters who have issues with their pellets shooting accurately let's say up to 110 yards but complaining about losing the precision at 120 yards give or take and at farther distances, this is what is happening to your pellets....How to resolve this issue you ask?
Estimate the BC at the distance where the pellet loses control (Use any Dopler chrony) and move this BC you found slightly ahead of max distance you will be shooting...Also calculate the pellet rotation at that distance so you known when is it that drag takes over spin. In other words: The destabilizing BC at the Aerodynamic Point Of Inflection (API) moved to farther distances slightly ahead from the max distances you will be shooting will determine the distance for the new API, AS SIMPLE AS THAT!
The other only alternative which is not my favorite, is to use a very low TR barrel and shoot at a higher velocity so the spin is not that high (less drift and turbulence)...The inconvenience is that this alternative would usually generate more drag derived from the lack of spin and it will come with its draw backs: Drift among them and less precision at longer distances; the BC at those farther distances would be lower given the fact that the projectile has been stabilized by drag for a longer period of time...
I will NOT be responding to bullies or to stupid questions/contradictions coming from "know it all wannabees" but will gladly answer any doubts.
Stay safe and hang in there, we will all come out of this crisis much better persons valuating what is important in life.
Please all receive my best regards,
AZ
