How much of a groups spread is accountable
- Thread starter 308sako
- Start date
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chuck furniss
Guest
This is a great subject that I have not seen any dicussion on.
I hope the knowlegable shooters on this forum will respond in mass to your question.
Chuck.
I hope the knowlegable shooters on this forum will respond in mass to your question.
Chuck.
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Cheechako
Guest
IMHO, parallax, focus, etc are shooter errors, not sighting errors. And I might even go so far as to say that eyesight is also a shooter error because it can be corrected.
After that, a lot will depend on the distance being fired and the scope magnification. For example, at 1000 yards with a 36-40X scope there should be little or no sighting error.
JMHO
Ray
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Bob Pastor
Guest
Group Dispersion
One thing not mentioned yet are the changing conditions during the bullets trek to the target. No matter what distance your shooting, being able to reliably read the changing conditions is paramount to group size and accuracy.
In most cases you will find that the top shooters are not only good at reading these conditions but they are Master Reloaders. Most matches are won or lost on the reloading bench. You have absolutely no chance of winning if you don't spend the time on your ammo.
One thing not mentioned yet are the changing conditions during the bullets trek to the target. No matter what distance your shooting, being able to reliably read the changing conditions is paramount to group size and accuracy.
In most cases you will find that the top shooters are not only good at reading these conditions but they are Master Reloaders. Most matches are won or lost on the reloading bench. You have absolutely no chance of winning if you don't spend the time on your ammo.
R
roninflag
Guest
group spread
308 SAKO- where i shoot there is quite a bit of wind. f class is shot off of a pedistal/ rest so i feel there is very little "aiming " error maybe a 1/10 of a minute or less. the rifles , ammo and scopes are capable of a great deal of precision 4/10 of a minute or less. the x ring on an f-class target is 1/2 minute. the rest is wind . the vertical is me and the gun; the horizontal is the wind. roninflag
308 SAKO- where i shoot there is quite a bit of wind. f class is shot off of a pedistal/ rest so i feel there is very little "aiming " error maybe a 1/10 of a minute or less. the rifles , ammo and scopes are capable of a great deal of precision 4/10 of a minute or less. the x ring on an f-class target is 1/2 minute. the rest is wind . the vertical is me and the gun; the horizontal is the wind. roninflag
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Cheechako
Guest
308
Since your Q was only about "sighting" errors, that is all that I commented on.
But Ron and Bob are correct. The difference between a winning shooter and the rest of the guys is the ability to read the conditions. If you go to a tournament with, say, 50 shooters, 35 of them have the equipment and capability of winning. Whoever reads the conditions the best that weekend will be the winner.
Of the other 15 guys, most will not have their loads tuned, will have equipment that has not been tuned, and will have scopes not focused or adjusted for parallax, and/or will have bad bench techniques - what I call shooter errors because all of these things can all be corrected.
Ray
Since your Q was only about "sighting" errors, that is all that I commented on.
But Ron and Bob are correct. The difference between a winning shooter and the rest of the guys is the ability to read the conditions. If you go to a tournament with, say, 50 shooters, 35 of them have the equipment and capability of winning. Whoever reads the conditions the best that weekend will be the winner.
Of the other 15 guys, most will not have their loads tuned, will have equipment that has not been tuned, and will have scopes not focused or adjusted for parallax, and/or will have bad bench techniques - what I call shooter errors because all of these things can all be corrected.
Ray
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chisqr
Guest
I would guess that Bob Pastor and roninflag are correct in the idea that optics contributes a relatively small part to the total group size, but it is still an interesting question because answering it points to how to answer related questions like "which is better, load A or load B". Also because it's one thing to speculate about something like this, it's something else to do a measurement and get some objective facts.
I can't directly say what the percentages are, but I can say something about how to measure them.
First we have to consider exactly what we mean by dispersion or group size. Most people use extreme spread to measure group size. Statistically extreme spread is a very poor way to measure group size. There are several problems with it which make it really only good for a very rough estimate of group size. It wouldn't really be mathematically valid to try to use extreme spread to answer this question. The best statistic for measuring the "true" group size is referred to as "width".
Assuming we are using width to measure true group size, the second thing to consider is how the optical and load factors combine to produce the group size we see. Imagine we had perfect optics (including the shooters vision), and variation in load was the only thing which made the group size larger than zero. Call the group size we would measure Sl. On the other hand, if only the optics contributed to the group size then we would measure a width of So.
The complication is that the group size we measure isn't simply Sl + So. That may seem strange, but you have to remember that the optical and load factors each contribute to a "smearing" of the overall group size. In a sense, Sl "smears" So, and vise versa. It turns out that the actual group size that you see is:
S = square_root ( Sl^2 + So^2 )
where Sl^2 is Sl squared, and So^2 is So squared. This also assumes that other contributions to the group size such as barrel harmonics can be neglected. The equation above could be modified to take these other things into account as well.
So now, to answer the original question about percentages we need two things. First, the true group size (width); and second, either Sl or So. Whichever we choose, the other can be calculated from the above equation. The desired percentages can then be calculated from So/S and Sl/S.
The width of the group, S, can be measured using target analysis to do the width calculation.
My guess is that it might be easier to get So by measuring the widths of groups for several different scopes with known optical specifications than by trying to get Sl. How load changes affect the group size is probably easier to measure because it is bigger, but the optics calculations needed to extract So from the group size would be easier and more accurate than what is needed to directly calculate Sl.
Another interesting thing that would come from such a study is an objective way to estimate the contribution of optics to the real group size on the target based on the optical specifications of different scopes -- although, I'm guessing the differences would be fairly small.
I can't directly say what the percentages are, but I can say something about how to measure them.
First we have to consider exactly what we mean by dispersion or group size. Most people use extreme spread to measure group size. Statistically extreme spread is a very poor way to measure group size. There are several problems with it which make it really only good for a very rough estimate of group size. It wouldn't really be mathematically valid to try to use extreme spread to answer this question. The best statistic for measuring the "true" group size is referred to as "width".
Assuming we are using width to measure true group size, the second thing to consider is how the optical and load factors combine to produce the group size we see. Imagine we had perfect optics (including the shooters vision), and variation in load was the only thing which made the group size larger than zero. Call the group size we would measure Sl. On the other hand, if only the optics contributed to the group size then we would measure a width of So.
The complication is that the group size we measure isn't simply Sl + So. That may seem strange, but you have to remember that the optical and load factors each contribute to a "smearing" of the overall group size. In a sense, Sl "smears" So, and vise versa. It turns out that the actual group size that you see is:
S = square_root ( Sl^2 + So^2 )
where Sl^2 is Sl squared, and So^2 is So squared. This also assumes that other contributions to the group size such as barrel harmonics can be neglected. The equation above could be modified to take these other things into account as well.
So now, to answer the original question about percentages we need two things. First, the true group size (width); and second, either Sl or So. Whichever we choose, the other can be calculated from the above equation. The desired percentages can then be calculated from So/S and Sl/S.
The width of the group, S, can be measured using target analysis to do the width calculation.
My guess is that it might be easier to get So by measuring the widths of groups for several different scopes with known optical specifications than by trying to get Sl. How load changes affect the group size is probably easier to measure because it is bigger, but the optics calculations needed to extract So from the group size would be easier and more accurate than what is needed to directly calculate Sl.
Another interesting thing that would come from such a study is an objective way to estimate the contribution of optics to the real group size on the target based on the optical specifications of different scopes -- although, I'm guessing the differences would be fairly small.
C
Cheechako
Guest
chisqr
Don't make this more complicated than it is. I think SAKO was asking the question as it relates to actual shooting and there, sighting errors are so small as to be inconsequental when the time comes for the A-Wards. Also, all of the truly competitive shooters will have sighting equipment that is equally good and tuned loads that are equally good and equipment (rifles, rests, etc) that are equally good, so the only difference will be in the individual shooters ability to read the conditions on that particular day.
JMHO
Ray
Don't make this more complicated than it is. I think SAKO was asking the question as it relates to actual shooting and there, sighting errors are so small as to be inconsequental when the time comes for the A-Wards. Also, all of the truly competitive shooters will have sighting equipment that is equally good and tuned loads that are equally good and equipment (rifles, rests, etc) that are equally good, so the only difference will be in the individual shooters ability to read the conditions on that particular day.
JMHO
Ray
LarryBartholome
Member
308sako,
Since you asked this question on an F-Class forum, I will say effectively zero percent of your group spread is attributable to eyesight or optics, if you are using top quality equipment and can see well enough to pass the driving test.
Group size due to load? You are looking at it the wrong way; if your shooter/rifle/ammo combination will not shot sub-1/2 moa groups out to 1k you have a problem with one or more of the three components. You need to troubleshoot the system until you locate all the problems.
As Bob and Ron have pointed out, in F-class, the name of the game is wind (and don’t forget mirage) doping. Keep in mind that all vertical is not due to the shooter and rifle/ammo and all horizontal is not due to the wind.
Since you asked this question on an F-Class forum, I will say effectively zero percent of your group spread is attributable to eyesight or optics, if you are using top quality equipment and can see well enough to pass the driving test.
Group size due to load? You are looking at it the wrong way; if your shooter/rifle/ammo combination will not shot sub-1/2 moa groups out to 1k you have a problem with one or more of the three components. You need to troubleshoot the system until you locate all the problems.
As Bob and Ron have pointed out, in F-class, the name of the game is wind (and don’t forget mirage) doping. Keep in mind that all vertical is not due to the shooter and rifle/ammo and all horizontal is not due to the wind.
Fred Bohl
Retired Engineer
For the most part I tend to agree with Cheechako that in real shooting conditions the wind and mirage and our ability to read them will trump most other considerations for top tier shooters particularly in competitive shooting situations. As Jackie Schmidt has often noted here, such abilities can be overwhelmed by a scope that will not hold point of aim.
Also, there are real optical limits inherent in the design of rifle scopes that can contribute significant limits to aiming precision. This directly affects group size when the group consists of individually aimed shots (as opposed to a "run" from a rail gun) or score (proximity to center) in score matches.
The first of these is the optical resolution limit (minimum sized resolvable feature) imposed by the objective diameter which is also the limit of aiming precision (circle of confusion). In popular target scopes the objective diameters provide resolution limits 0.048 to 0.035 MOA. While that seems small, consider that in point blank benchrest winning groups are usually under 0.20 MOA and the goal is under 0.10 MOA in great conditions. This would put the 30% contribution estimate by 308sako in the ball park.
The second design factor is for the scope to provide sufficient magnification for the user’s visual acuity to be able to get an image to the resolution limit. Another design requirement is for optical quality sufficient for distortions to be well under the resolution limit. These two are usually well within the capability of most quality target scopes.
For those interested in the more technical details of popular target scopes, please see the attached.
Also, there are real optical limits inherent in the design of rifle scopes that can contribute significant limits to aiming precision. This directly affects group size when the group consists of individually aimed shots (as opposed to a "run" from a rail gun) or score (proximity to center) in score matches.
The first of these is the optical resolution limit (minimum sized resolvable feature) imposed by the objective diameter which is also the limit of aiming precision (circle of confusion). In popular target scopes the objective diameters provide resolution limits 0.048 to 0.035 MOA. While that seems small, consider that in point blank benchrest winning groups are usually under 0.20 MOA and the goal is under 0.10 MOA in great conditions. This would put the 30% contribution estimate by 308sako in the ball park.
The second design factor is for the scope to provide sufficient magnification for the user’s visual acuity to be able to get an image to the resolution limit. Another design requirement is for optical quality sufficient for distortions to be well under the resolution limit. These two are usually well within the capability of most quality target scopes.
For those interested in the more technical details of popular target scopes, please see the attached.
308sako
New member
Aside from varying conditions and poor loads,
First let me thank the responders for their experiences and extremely well thought out answers. I am trying to focus on the shooter, as I shoot against myself rather than in competition. The question arose from my observations which some might simply refer to as calling a shot. Meaning that I think at the moment of sear break the crosshairs weren’t quite exactly where they were supposed to be, but the bullet landed where it should… or Heaven forbid the opposite!
Edited to add: I guess I am forced to add a third variable here which is shooter induced error. Be it poor form, or just a lack of consistant hold/cheek weld. I kind of feel that this is a portion of the sighting errors which I am aluding to in part one. Thanks all.
Bob Pastor’s “One thing not mentioned yet are the changing conditions during the bullets trek to the target. No matter what distance your shooting, being able to reliably read the changing conditions is paramount to group size and accuracy.”
I can’t disagree with the statement, but am trying to focus on the shooter’s contribution to error as opposed to environmental effects. That’s why I have arbitrarily declared the best of loads and glass.
Chrisqr
Wow, just wow!
First let me thank the responders for their experiences and extremely well thought out answers. I am trying to focus on the shooter, as I shoot against myself rather than in competition. The question arose from my observations which some might simply refer to as calling a shot. Meaning that I think at the moment of sear break the crosshairs weren’t quite exactly where they were supposed to be, but the bullet landed where it should… or Heaven forbid the opposite!
Edited to add: I guess I am forced to add a third variable here which is shooter induced error. Be it poor form, or just a lack of consistant hold/cheek weld. I kind of feel that this is a portion of the sighting errors which I am aluding to in part one. Thanks all.
Bob Pastor’s “One thing not mentioned yet are the changing conditions during the bullets trek to the target. No matter what distance your shooting, being able to reliably read the changing conditions is paramount to group size and accuracy.”
I can’t disagree with the statement, but am trying to focus on the shooter’s contribution to error as opposed to environmental effects. That’s why I have arbitrarily declared the best of loads and glass.
Chrisqr
Wow, just wow!
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LarryBartholome
Member
F-Class?
308sako,
Please don’t take offence but, I just have to ask this…why ask your questions on the F-Class forum if you don’t shoot F-Class? The point blank or 1k BR sections I can understand but F-Class.
308sako,
Please don’t take offence but, I just have to ask this…why ask your questions on the F-Class forum if you don’t shoot F-Class? The point blank or 1k BR sections I can understand but F-Class.
308sako
New member
No offense taken!
I am trying to work my way up to F-class shooting which is available in my area. F-class is a style of shooting with which I am familiar, it is the competition which I have not participated in. I think that the question would certainly be valid elsewhere.
LarryBartholome
Member
Welcome to F-Class
308sako,
I wish you had said that before. Do yourself a favor and just go to a match and jump right in. The water is fine and everyone is nice. Just tell the match director it is your first time and to be gentle. Try mid-range first if you have a choice. Don’t worry about how you will do, just enjoy it. Welcome to F-Class.
308sako,
I wish you had said that before. Do yourself a favor and just go to a match and jump right in. The water is fine and everyone is nice. Just tell the match director it is your first time and to be gentle. Try mid-range first if you have a choice. Don’t worry about how you will do, just enjoy it. Welcome to F-Class.
C
chisqr
Guest
Along with the other useful information, the resolution limits provided by Fred Bohl are essentially the width numbers that I called So.
There are lots of small, but non-zero, effects like this that contribute to group size. The closer two competitors are in ability, the more important small effects like this become. This is precisely why people spend so much money on equipment to get a small improvement. Whether or not a particular effect is negligible in a practical sense, can be stated objectively in terms of the numbers which separate two competitors. Awards are based on numbers.
LarryBartholome's statement about trouble shooting the system is very apt. 308sako's question goes to isolating and quantifying the different parts of the system which is the first step in efficient trouble shooting. Getting objective answers takes what it takes -- and the smaller the effect the more effort required to get an answer. But the importance of small effects and the effort required to understand them is just a consequence of how far competitive shooting has evolved and the fact that it continues to evolve.
There are lots of small, but non-zero, effects like this that contribute to group size. The closer two competitors are in ability, the more important small effects like this become. This is precisely why people spend so much money on equipment to get a small improvement. Whether or not a particular effect is negligible in a practical sense, can be stated objectively in terms of the numbers which separate two competitors. Awards are based on numbers.
LarryBartholome's statement about trouble shooting the system is very apt. 308sako's question goes to isolating and quantifying the different parts of the system which is the first step in efficient trouble shooting. Getting objective answers takes what it takes -- and the smaller the effect the more effort required to get an answer. But the importance of small effects and the effort required to understand them is just a consequence of how far competitive shooting has evolved and the fact that it continues to evolve.
M
mysticplayer
Guest
308SAKO, takes Larry's advice and just go shoot a match. The first times you drive a few X's, you're hooked. Then the fun really begins 
Most of my matches are at 300m, some out to 600m. I try and get out on calm days at first light so there is little mirage or wind.
When I test my loads, I am looking for as little vertical dispersion as possible. This is also a great test of my rests and tech. My goal is 1/2" at 300m, 1.5" at 600m. Less is of course better.
My groups look like sideways footballs as windage is what I will drive. I don't want to add vertical in mechanical error. That would be too much for me to dope.
For optics, you need to be able to see the target. I use a 24X scope. Don't feel the need for more as mirage drives me insane. However, the resolution and clarity allows me to 'see' about 3/16" at 300m. That is all I will ever need to dope conditions for the X ring.
I prefer the much wider field of view as this gives me more chance to see the conditions. This matters to me more then another 1/16" on the target and missing a wind change.
As has been said many times, F class is won by the shooter that can drive the best, not by the best equipment.
If the rifle/optics/load are consistent enough for the X ring, the rest is up the nutt behing the trigger. When I am in a match, I have to believe that my shot arrived due to conditions. I adjust from that. I trust that my gear/shooting is consistent enough to put them into the X ring. If the shot goes somewhere else, I have to correct as this is a condition change that I am missing.
Everytime, I have not trusted myself and thought it was me, I missed again.
Jerry
Most of my matches are at 300m, some out to 600m. I try and get out on calm days at first light so there is little mirage or wind.
When I test my loads, I am looking for as little vertical dispersion as possible. This is also a great test of my rests and tech. My goal is 1/2" at 300m, 1.5" at 600m. Less is of course better.
My groups look like sideways footballs as windage is what I will drive. I don't want to add vertical in mechanical error. That would be too much for me to dope.
For optics, you need to be able to see the target. I use a 24X scope. Don't feel the need for more as mirage drives me insane. However, the resolution and clarity allows me to 'see' about 3/16" at 300m. That is all I will ever need to dope conditions for the X ring.
I prefer the much wider field of view as this gives me more chance to see the conditions. This matters to me more then another 1/16" on the target and missing a wind change.
As has been said many times, F class is won by the shooter that can drive the best, not by the best equipment.
If the rifle/optics/load are consistent enough for the X ring, the rest is up the nutt behing the trigger. When I am in a match, I have to believe that my shot arrived due to conditions. I adjust from that. I trust that my gear/shooting is consistent enough to put them into the X ring. If the shot goes somewhere else, I have to correct as this is a condition change that I am missing.
Everytime, I have not trusted myself and thought it was me, I missed again.
Jerry
308sako
New member
The mental aspect to good shooting
Chrisqr, et al, I sincerely wish to thank the posters above, and any below should that occur. The highly advanced life forms which I have discovered lurking here in Fclass are well beyond the norm in their individual and cumulative understandings of Dr Mann's theories. Having posted the question elsewhere for the masses of trigger jerkers I assure you that no where is the refined art of the squeeze more prevalent than here.
I appreciate the effort taken to help me further my shooting, and possibly one day attain a degree of self esteem which would allow me to consider myself worthy of asking a second question or two. To that end I will go and consume another brick or two of primers and make a few unorganized observations which will lead me down this road once again.
I am aware that I do not tend to think exactly like the next shooter, hence my way of fractionalizing the problem and seeking a remedy to poor performance, be it equipment or personal in origin.
Once again thank you all.
D
Chrisqr, et al, I sincerely wish to thank the posters above, and any below should that occur. The highly advanced life forms which I have discovered lurking here in Fclass are well beyond the norm in their individual and cumulative understandings of Dr Mann's theories. Having posted the question elsewhere for the masses of trigger jerkers I assure you that no where is the refined art of the squeeze more prevalent than here.
I appreciate the effort taken to help me further my shooting, and possibly one day attain a degree of self esteem which would allow me to consider myself worthy of asking a second question or two.
To that end I will go and consume another brick or two of primers and make a few unorganized observations which will lead me down this road once again. I am aware that I do not tend to think exactly like the next shooter, hence my way of fractionalizing the problem and seeking a remedy to poor performance, be it equipment or personal in origin.
Once again thank you all.
D
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J
JeffVN
Guest
308 Sako
you need to come out to Boulder City R & P this Sunday at 7:30 am; we shoot what we call palma practice, including f-class PRACTICE from 800, 900, and 1K. it is a PRACTICE Match, meaning no official score, only you keeping your own score. We shoot these every month, cost is $7.00 for non-Boulder members. Its a good time to get some of that experience you may be/are looking for without any match "pressures."
Jeffvn
you need to come out to Boulder City R & P this Sunday at 7:30 am; we shoot what we call palma practice, including f-class PRACTICE from 800, 900, and 1K. it is a PRACTICE Match, meaning no official score, only you keeping your own score. We shoot these every month, cost is $7.00 for non-Boulder members. Its a good time to get some of that experience you may be/are looking for without any match "pressures."
Jeffvn
Fred Bohl
Retired Engineer
308sako
I tend to see your “way of fractionalizing the problem” as a very rational way to approach becoming a better shooter. Great shooting, particularly for score or individually aimed shots for group (pickers versus runners), is made up a set of many acts (each including a precise set of steps) that all have to be mastered and then executed nearly identically each time. While some can pick up the techniques required for most of the acts easily, some require an understanding of the equipment and science of the act.
A common emphasis in the threads on this forum is on the importance of practice or trigger time particularly in competition and I fully support that you will not become a great shooter without it. However, practicing incorrect techniques is counter productive. Go to matches and talk to good shooters and study the writings of the good shooters to try to learn from their mistakes and get started in a good direction. Also study the applicable sciences including but not limited to ballistics.
For example, I find it amazing how little understanding there is of the science behind optics and visual perception by even very successful competitive shooters. Considering how important they are to our success, most shooters have only a rudimentary understanding of the mechanics of their scopes, even less of the physics of optics involved and almost nothing about the way the human visual system works particularly in this application. The amount of powder bullets and barrels consumed by overcoming this lack of knowledge by “shooting to learn” must be huge.
I do not pretend to an expert on anything, but I have done my homework and put more rounds down range than I’d like to admit in 55 years of shooting. I probably have most useful current results of my study-experiment-practice routine for your purposes in the area of spotting scopes and rifle scopes. If you want to discuss that area either PM me or ask here. I believe in sharing the knowledge my sweat, tears and costs have brought so not everyone has to do all themselves.
I tend to see your “way of fractionalizing the problem” as a very rational way to approach becoming a better shooter. Great shooting, particularly for score or individually aimed shots for group (pickers versus runners), is made up a set of many acts (each including a precise set of steps) that all have to be mastered and then executed nearly identically each time. While some can pick up the techniques required for most of the acts easily, some require an understanding of the equipment and science of the act.
A common emphasis in the threads on this forum is on the importance of practice or trigger time particularly in competition and I fully support that you will not become a great shooter without it. However, practicing incorrect techniques is counter productive. Go to matches and talk to good shooters and study the writings of the good shooters to try to learn from their mistakes and get started in a good direction. Also study the applicable sciences including but not limited to ballistics.
For example, I find it amazing how little understanding there is of the science behind optics and visual perception by even very successful competitive shooters. Considering how important they are to our success, most shooters have only a rudimentary understanding of the mechanics of their scopes, even less of the physics of optics involved and almost nothing about the way the human visual system works particularly in this application. The amount of powder bullets and barrels consumed by overcoming this lack of knowledge by “shooting to learn” must be huge.
I do not pretend to an expert on anything, but I have done my homework and put more rounds down range than I’d like to admit in 55 years of shooting. I probably have most useful current results of my study-experiment-practice routine for your purposes in the area of spotting scopes and rifle scopes. If you want to discuss that area either PM me or ask here. I believe in sharing the knowledge my sweat, tears and costs have brought so not everyone has to do all themselves.
308sako
New member
Jeff, Thanks for the invite, but we have company in town till Tueday.
Fred B, You are among the finest of gentlmen shooters, your kind offer is appreciated.
D