ES and SD Question
- Thread starter jeguia
- Start date
Yep Jim....Norman has a lot to learn. He just lucked into his results at the last F-class LR nationals.
More than one to get done, is my point...... jim
I don't know Jim - but this is what I found when searching this site
https://www.accurateshooter.com/competition/ohara-sets-1000-yard-ibs-agg-records/
Average joe
Gold $$ Contributor
From what I read, Jim & Norm are in complete agreement ....... and both are excellent shooters.
Ned Ludd
Silver $$ Contributor
There are a fair number of people worth listening to that post here, and Norm is also most definitely one of them. These kind of wee-wee contests are really not very useful for anyone.
jeguia - to begin with, some background in statistical analyisis is warranted if ES/SD numbers are to have any real meaning. Assuming you are already in possession of such background, the next consideration is the discipline you're shooting. ES/SD will have different meanings and relative importance to shooters in different disciplines. For example, you will likely find more F-Class shooters that are concerned about ES/SD, largely due to the long strings of fire (20+ shots).
One of the simplest ways to start to get a handle on the effect of ES/SD is to run some numbers in your favorite ballistics program. I typically use JBM online (http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi). If you know your load's muzzle velocity +/- SD, you can input these values into a ballistic calculator to get a predicted effect on vertical (point of impact) at some specified distance such as 600 or 1000 yd.
Note that these ballistic calculator predictions typically do not take the aforementioned "positive compensation" into account. FWIW - positive compensation is really about barrel harmonics and muzzle launch angle. In a well-tuned load, the bullets that are moving slightly faster will leave the barrel slightly earlier in the harmonic cycle when the muzzle is on the upswing, but not at the top of its arc of travel. Slightly faster bullets will therefore exit the bore muzzle/bore when it is pointing at a slightly shallower upward angle. A bullet that is moving slightly slower will take longer to reach the muzzle, thereby exiting slightly later in the barrel harmonic cycle when the bore is pointing upward at a higher launch angle. Because the slightly faster bullets leave with a shallower launch angle and the slightly slower bullets leave with a higher launch angle, they arrive at the same vertical spot on a target at some specified distance where the load was tuned in. In other words, launch angle compensates for slight differences in bullet velocity in terms of vertical at the target. As I understand it, positive compensation works optimally within a velocity range of perhaps 15 to 20 fps.
You will find many BR shooters here that take advantage of positive compensation for loading and shooting tiny groups at 1000 yd. You will also see many of them post that their very best loads (in terms of accuracy/precision) did not have the lowest ES/SD values. In other words, they often find that loads with excellent ES/SD values of perhaps 5.0/2.0 fps don't necessarily group as well as (or any better than) loads with with more moderate ES/SD values of perhaps 15/7.0. In my mind, this is proof that we (or perhaps it is just me) don't understand everything there is to know about the effect of positive compensation. Here's why: if PC works optimally within a maximum velocity range of ~15 to 20 fps, it shouldn't make any difference whether the ES/SD was 15/7.0, or 5.0/2.0. Muzzle launch angle should compensate for velocity differences within the optimal velocity range equally well, regardless. Yet I have read a number of posts by BR shooters indicating that their loads with very low ES/SD values were often not nearly as good as the ones with ES/SD values slightly higher. Clearly something in addition to positive compensation is at work, or else the process is not fully understood.
The impact of ES/SD values in F-Class shooting is a different animal, primarily because we shoot long strings of fire (i.e. 20+ shots) over the course of 22-25 minutes. Barrel heating and velocity excursions are a consideration because of this. Further, we want good accuracy/precision in an F-Class load. However, it doesn't have to be quite up to BR standards, because the wind will generally be the limiting factor over the long strings of fire. Having a load that will shoot groups in the 0.1s or 0.0s isn't worth any more than one that will shoot a quarter MOA when the wind conditions are sufficient to put you into the 7-ring if you miss a wind call. In other words, it's all about the limiting source of error (i.e. the largest source of error). In most F-Class matches, you will lose more points to missed wind calls than anything else. Thus, wind becomes the limiting source of error. On a dead calm day, it would be fairly simple to shoot cleans with a load that shot 0.1 MOA, or one that shot 0.25 MOA, because the precision of the load wasn't the limiting source of error.
Earlier in this thread, XTR (Wade) provided you with some ES/SD values in the range of what many F-Class shooters are looking for and can readily acquire through meticulous reloading practices. I would suggest you play around with those numbers using a ballistics calculator to obtain some crude estimates (i.e. - estimates that don't take PC into account) of the effect of velocity variance on POI at a distance. It may give you a better feel for what they mean. Then I would suggest forgetting about that information and simply reloading your F-Class rounds as carefully and meticulously as you can to achieve the lowest ES/SD possible with the equipment you have available to you. If you can load with ES/SD values of something like 6.0/1.5 fps, you will do well. If you can only achieve values of perhaps 15/8.0, you will still do well. In neither of those cases will your ammunition ES/SD be the limiting source of error. If you can only load with ES/SD of 60/20, then you may have a problem, especially at longer range. Exactly where in between those different sets of values the cutoff lies is what you're really asking, but there is no definitive answer. So we try to employ reloading practices that will keep the ES/SD as low as we possibly can.
jeguia - to begin with, some background in statistical analyisis is warranted if ES/SD numbers are to have any real meaning. Assuming you are already in possession of such background, the next consideration is the discipline you're shooting. ES/SD will have different meanings and relative importance to shooters in different disciplines. For example, you will likely find more F-Class shooters that are concerned about ES/SD, largely due to the long strings of fire (20+ shots).
One of the simplest ways to start to get a handle on the effect of ES/SD is to run some numbers in your favorite ballistics program. I typically use JBM online (http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi). If you know your load's muzzle velocity +/- SD, you can input these values into a ballistic calculator to get a predicted effect on vertical (point of impact) at some specified distance such as 600 or 1000 yd.
Note that these ballistic calculator predictions typically do not take the aforementioned "positive compensation" into account. FWIW - positive compensation is really about barrel harmonics and muzzle launch angle. In a well-tuned load, the bullets that are moving slightly faster will leave the barrel slightly earlier in the harmonic cycle when the muzzle is on the upswing, but not at the top of its arc of travel. Slightly faster bullets will therefore exit the bore muzzle/bore when it is pointing at a slightly shallower upward angle. A bullet that is moving slightly slower will take longer to reach the muzzle, thereby exiting slightly later in the barrel harmonic cycle when the bore is pointing upward at a higher launch angle. Because the slightly faster bullets leave with a shallower launch angle and the slightly slower bullets leave with a higher launch angle, they arrive at the same vertical spot on a target at some specified distance where the load was tuned in. In other words, launch angle compensates for slight differences in bullet velocity in terms of vertical at the target. As I understand it, positive compensation works optimally within a velocity range of perhaps 15 to 20 fps.
You will find many BR shooters here that take advantage of positive compensation for loading and shooting tiny groups at 1000 yd. You will also see many of them post that their very best loads (in terms of accuracy/precision) did not have the lowest ES/SD values. In other words, they often find that loads with excellent ES/SD values of perhaps 5.0/2.0 fps don't necessarily group as well as (or any better than) loads with with more moderate ES/SD values of perhaps 15/7.0. In my mind, this is proof that we (or perhaps it is just me) don't understand everything there is to know about the effect of positive compensation. Here's why: if PC works optimally within a maximum velocity range of ~15 to 20 fps, it shouldn't make any difference whether the ES/SD was 15/7.0, or 5.0/2.0. Muzzle launch angle should compensate for velocity differences within the optimal velocity range equally well, regardless. Yet I have read a number of posts by BR shooters indicating that their loads with very low ES/SD values were often not nearly as good as the ones with ES/SD values slightly higher. Clearly something in addition to positive compensation is at work, or else the process is not fully understood.
The impact of ES/SD values in F-Class shooting is a different animal, primarily because we shoot long strings of fire (i.e. 20+ shots) over the course of 22-25 minutes. Barrel heating and velocity excursions are a consideration because of this. Further, we want good accuracy/precision in an F-Class load. However, it doesn't have to be quite up to BR standards, because the wind will generally be the limiting factor over the long strings of fire. Having a load that will shoot groups in the 0.1s or 0.0s isn't worth any more than one that will shoot a quarter MOA when the wind conditions are sufficient to put you into the 7-ring if you miss a wind call. In other words, it's all about the limiting source of error (i.e. the largest source of error). In most F-Class matches, you will lose more points to missed wind calls than anything else. Thus, wind becomes the limiting source of error. On a dead calm day, it would be fairly simple to shoot cleans with a load that shot 0.1 MOA, or one that shot 0.25 MOA, because the precision of the load wasn't the limiting source of error.
Earlier in this thread, XTR (Wade) provided you with some ES/SD values in the range of what many F-Class shooters are looking for and can readily acquire through meticulous reloading practices. I would suggest you play around with those numbers using a ballistics calculator to obtain some crude estimates (i.e. - estimates that don't take PC into account) of the effect of velocity variance on POI at a distance. It may give you a better feel for what they mean. Then I would suggest forgetting about that information and simply reloading your F-Class rounds as carefully and meticulously as you can to achieve the lowest ES/SD possible with the equipment you have available to you. If you can load with ES/SD values of something like 6.0/1.5 fps, you will do well. If you can only achieve values of perhaps 15/8.0, you will still do well. In neither of those cases will your ammunition ES/SD be the limiting source of error. If you can only load with ES/SD of 60/20, then you may have a problem, especially at longer range. Exactly where in between those different sets of values the cutoff lies is what you're really asking, but there is no definitive answer. So we try to employ reloading practices that will keep the ES/SD as low as we possibly can.
He is the real deal !! I was there when set those records.
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