Tag Archives: Long Range Shooting

RELOADERS CORNER: SD Pt. 2

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Here’s how Standard Deviation calculations can figure in ammo decisions (or not…) READ MORE…

Glen Zediker

Seems like the last couple of articles on load testing and velocity data got some pretty good responses and attention, and so that means there’s more! Of course there is…

As said, Standard Deviation (SD) plotted out forms a bell curve. A bell curve indicates the “probability density” of the normal distribution, or range, for something like velocity consistencies. For our purposes that’s the likely speed of the next shot.

Chances are outstanding that running all the numbers gotten from a chronograph session will plot into what’s called a “normal curve.” Like any normal bell curve, it gets divided into three segments and values, and these divisions are the “standard deviations.” And remember it is “a” standard deviation.

(I’ve said many a time that I’m sho no mathematician, and I am aware that there’s more and different ways to apply and model a curve, and to manipulate standard deviation results for different applications, but I’m trying to keep it more simple and use this “normal curve” for examples, it’s also called “population standard deviation.”)

We’ve been working with the right-respectable SD example of 12.

standard deviation curve
Here’s the same old curve I’ve been using, but at least in a different color!

Assuming that normal curve, the distribution of “some number” of shots is forecasted like so: some 68 percent will lie within 1 standard deviation of the mean, about 95 percent lie within 2, and over 99 percent lie within 3 standard deviations. Again, since our SD is 12, then about 68 percent (approx. 2 out of 3) of all “next shots” will be +/- 12 feet per second. Since, though, the curve is in threes, that means that a scant number of the shots pose a chance for +/- 24 and some much (much) smaller chance remains for some shots to go to +/- 36. SD estimates how likely it is for those “head-scratchers” to show up, and also what might be the most realistic extreme any shot can deviate.

Data is a record of numbers and I do know that there’s 100-percent chance that the highest and lowest velocities collected for an SD calculation did, in fact, happen. To me, that’s what matters. No matter what the collected shot results calculated into for an SD, those were the two that represent the highest and lowest prints on the target.

It’s mathematically not possible for an SD to be higher than the greatest single measured deviant, and an SD can sho be lower than any single “bad” shot. Given how it’s calculated, along with how many samples contributed to the calculation, it’s plain that the nearer the majority are to themselves the less impact a bad one or more has. The more input the better.

ppc
Cartridge choice has a whopping lot to do with it! Some cartridges are seemingly destined (designed really) to produce better velocity consistency. Many magnums, for instance, are notoriously sporadic, while others, like the 6XC or one of the PPC cartridges (shown), seem to deliver constant velocities without a lot of special effort. It all has to do with internal ballistics and “efficiency,” and architectural analysis I don’t claim to understand, but I do know that’s one of the reasons 6XC holds the NRA High Power Rifle Long Range record, at the hands of David Tubb.

Many of us have heard or read the frequently-sung “…seen good accuracy with high SDs…” And we’ve probably also all decided that can’t be taken at literal value. Well, it can’t. Three things: what is “good accuracy” to this fellow, at which distance were the groups printed, and what’s he say is “high,” because without knowing these things there’s no accounting for the accuracy, believability, or interpretative definitiveness of what’s being said. So I say it’s 12. A 12 should not be responsible for a points loss, also considering the edge limits of usual group size. Getting into more and more numbers derived from more and more “what if’s” plotting out bullet trajectories and wind drift amounts, and, always assuming a consistent bullet ballistic coefficient demonstration (also not likely) running “12” through all these mathematical-hypothetical scenarios will show that 12 doesn’t lose many, if any, points.

One last that isn’t really a strong point, but is a point… If we’re shooting something like a .223 Rem. then a half-grain is about 40 feet per second. If that 12 SD shows its worst and pops one out +36 feet per second, to me that represents something akin to a pressure spike (logic dictates that more velocity had something to do with more pressure). I know my loads are running a tad amount edgy, and seeing a small velocity variation is likewise a tad amount more reassuring that a primer won’t go over the edge.

tubb 1000 yard clean
Here’s the ultimate result of low velocity deviations. It’s up to the shooter to apply the left and right, but it’s up to the ammo to keep vertical stringing to a minimum. David Tubb does a stellar job on both. 1000 yards, fired prone with a scope. 6XC.

TESTING TIP
If you’re testing much beyond 200 yards, and especially beyond 300, pay no mind to the left and right, but keep a close watch on the up and down. In ideal conditions, groups are supposed to be round (I’m convinced they’re actually square, but there’s no need to go into that). If there’s any wind, don’t even try to correct for it (as long as impacts are on the target). I honestly don’t need a chronograph to confirm load consistency if I’m seeing small vertical dispersions. I’ll already have speed-checked the load I’m down on the mat with, and, again, I’m just wanting to see how level I get my perforations. If I come out with a 600-yard group that’s a foot wide but only three inches tall, I’m happy.

6 TIPS FOR LOWER SDs
Aside from finding the perfect and magical load combination, ha, there are a few things that do seem to help tighten shot-to-shot velocity deviations. They’ve all be talked all the way through and back again in this space in other articles, but, considered ultimately that this is the overall effect they have, here they are again:

One. Primer seating: fully seated onto a flat pocket bottom.

Two. Consistent propellant charge: weigh the charges if metering isn’t dead-on.

Three. Ignition efficiency: consider trying that inside flash hole deburring routine…

Four. Consistent case neck sizing, and, believe it or not, about 0.003 worth of “tension.” Don’t go too light…

Five. Temperature insensitivity: choose propellants that exhibit stability under extremes.

Six. Balance: strive to find a propellant that fills the case, but “loosely” (no compressed charges); even more, avoid an overage of air space. These both allow too much variance in ignition pattern.

inside deburring tool

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: Standard Deviation

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Improving longer-range accuracy has a lot to with consistent bullet velocities. First comes understanding it! Here’s a start on it… KEEP READING

chronograph

Glen Zediker

It’s springtime (finally) and one of the things on your list might be working up a load for a new rifle, or new bullet. I’ve talked about testing processes and procedures, and also some about those bullets, and especially those with higher ballistic coefficients. The more aerodynamic bullet, by itself, is no guarantee of a smaller group (and whether you’re shooting one shot or 20 shots, you’re always shooting a group…).

To make the “magic” of a high-BC bullet come to life, they all need to be arriving at the destination at really close to the same speed. On target, that’s all about elevation consistency. It’s pretty commonly accepted among long-range competitive shooters that points losses come more from errant high and low impacts than from missed wind calls. High-BC bullets traveling at more consistent speeds reduces dispersions in all directions. But only if they’re traveling at consistent velocities!

The first step to improving velocity consistency is getting a good way to measure it. That there would be a chronograph. Nowadays especially, there are a number of simple-to-use and inexpensive chronographs available, that are accurate. Some have more features, which mostly revolve around providing printouts, digital records, and calculations, but what matters most (to me at least) is one that lets me easily read the velocity of each shot.

Check Misdouth offerings HERE

MagnetoSpeed
The newer barrel-mounted electro-magnetic chronographs make it really easy. I like the idea of being able to chronograph from shooting position, not just from a benchrest. This is a MagnetoSpeed.

So. What’s next is understanding the terms associated with this area of data-gathering.

“Standard deviation” (SD) is the most common measure of shot-to-shot consistency. It reflects on the SD reflects on the anticipated consistency of bullet velocities (some number of recorded velocities). The “standard” part reflects on a sort of an average of the rounds tested.

[Phrases like “sort of” upset mathematically-oriented folks, so here’s the actual definition: SD is the square root of the mean of the squares of the deviations. More in a bit.]

I pay less attention than many to standard deviation because: I don’t think standard deviation is near as important as is the “range,” which is the lowest and highest speeds recorded. Another that matters is “extreme spread,” which, by definition, is the difference between this shot and the next shot. I watch the speed on each shot. I compare this one to the next one and to the last one, and, as said, find the highest and the lowest.

Why? Well because that’s how I shoot tournament rounds. This one, then another, and another. A low velocity difference means that the accuracy of my judgment of my own wind call has some support.

standard deviation
Standard deviation calculation forms a bell curve. The steeper and narrower the apex of the bell, the narrower the fluctuations were. But there’s always a bell to a bell curve and the greatest deviations from desired standard are reflected in this portion of the plot. Depending on the number of shots that went into the SD calculation, these deviations may be more or less notable than the SD figure suggests. So? Watch each shot. That’s the way to know how a load performs with respect to velocity consistency. SD allows you to estimate how likely it is for “outliers” to show up.

A load that exhibits a low SD is not automatically going to group small, just because a low SD. I’ve had Benchrest competitors tell me that sometimes their best groups don’t come with a low-SD load, but do not apply that to greater distance! At 100 yards a bullet’s time of flight and speed loss are both so relatively small that even what some might call a big variation in bullet velocities (+/-25 fps or so) isn’t going to harm a group, not even the tiny groups it takes to be competitive in that sport. On downrange, though, it really starts to matter. (And keep in mind that “it” is a reference to velocity consistency, whether denoted by SD or otherwise.)

For an example from my notes: Sierra 190gr .308 MatchKing. Its 2600 fps muzzle velocity becomes 2450 at 100 yards and 1750 at 600 yards. (These numbers are rounded but serve for a example.)

If we’re working with a just awful 100 fps muzzle velocity change, that means one bullet goes out at 2550 and the next leaves at 2650, in the worst-case. The first drifts about 28 inches (let’s make it a constant full-value 10-mph wind to keep it simple) and the next slides 26 inches. But! Drop… That is THE factor, and here’s where inconsistent velocities really hurt. With this 190, drop amounts over a 100 fps range are about three times as great as drift amounts. This bullet at 2600 muzzle velocity hits 5-6 inches higher or lower for each 50 fps muzzle velocity difference. That’s going to cost on target, big time. And it gets way, way (way) worse at 1000 yards. Velocity-caused errors compound on top of “normal” group dispersion (which would be group size given perfect velocity consistency). Now, it’s unusual for a wind to be full-value and dead constant, so on-target left and right displacement is even relatively less — but elevation displacement is consistent regardless.

So, my 100 fps example is extreme, but half of that, or a quarter of that, still blows up a score, or an important hit on a target.

propellant charge consistency
This is probably the most influential factor in improving SD: consistent propellant charge. It’s not only that each case has an identical powder load, though, because primer factors, and finding the right combination ultimately is why we do all the testing…

So what’s a tolerable SD? 12. There have been, rest assured, much calculation to lead  up to that answer. That’s the SD that “doesn’t matter” to accuracy, meaning it’s not going to be the leading factor in a miss. It’s more than I’ll accept for a tournament load, but for those I’m looking for an extreme spread never more than 10 fps (the range might be higher, but now we’re just mincing terms). More later…

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.

REVIEW: A Long-Range Story: Hornady 4DOF Ballistics Calculator

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Here’s a new ballistics calculator that takes four important ballistic factors into account, not just BC, to provide radically more precise calculated bullet flight figures. Here’s how it works…

4DOF

by Richard Mann

The new Hornady 4DOF ballistics calculator is so precise because it combines what Hornady calls the Four Degrees of Freedom. In other words, it takes into account windage, elevation, range, and angle of attack to generate a drag coefficient.

4 DOF

Recently, a few magazine editors visited for a week. Egos were on display and opinions were as thick as brass on the range at Gunsite Academy. The purpose of this get-together was to test about two dozen rifles, some purpose-built for connecting at extended distances. I have access to a 1,700-yard range and we spent the day there. My 17-year-old son, Bat, served as the official “range rat.”

After our 500-yard testing was complete, I told my associates I needed to get the DOPE (data of previous engagement) on my son’s African rifle. This would save a trip back to the range and give him some time behind the gun as payment for the support role he’d been filling.

The previous evening we had chronographed the Hornady Precision Hunter ELD-X load for the 6.5 Creedmoor my son would be using. That velocity, along with the bullet and related specifics were entered into Hornady’s 4DOF ballistic calculator, which is available online. I’d printed the results and our goal was to confirm elevation come-ups out to 500 yards. Amazingly, this was done with 5 shots; my son connected center target at 100, 200, 300, 400, and 500 yards. The data generated by the Hornady 4DOF calculator was spot-on.

Bat was having fun and shooting well, and since he now had the attention of the visiting editors, I figured, what the heck, he might as well try 700 yards. His first shot at 700 was about 2 inches high so he made a .25-MOA correction and fired again. Center hit! Now he really had their attention.

The next farthest target was at what I was told was 1,100 yards, and Bat asked if he could take a poke. I was skeptical and worried he’d blow the impression he’d already made on these experts, but figured the boy deserved a chance. The Hornady 4DOF ballistics calculator data called for a 38.25-MOA adjustment at 1,100 yards. I got on the spotting scope and told him, “Send it.” He did, and he missed high, by what appeared to be several feet.

I Instructed Bat to walk the reticle in the Bushnell 2.5-10X Engage riflescope — yes, this was a 10X riflescope — down 1 MOA at a time. At 3 MOA below center, I called the shot just left. (Wind is a terrible thing at 1,100 yards.) My instructions were to keep the same elevation hold but to also hold 2 MOA off the right edge. He pulled the trigger six times and achieved six hits. The onlookers were stunned, I however, was confused.

With the 4 DOF calculator from Hornady you can input your data and go to the range with total confidence it will be precise. Of course, remember, garbage in, garbage out. You have to input the right information.

4DOF printout

How could the Hornady 4DOF ballistics calculator data be so correct out to 700 yards and be off so much at 1,100? A range finder and a return to the Hornady 4DOF ballistics calculator answered the question. Instead of 1,100 yards, the target was at 1,048 yards. Resetting the Hornady 4DOF calculator to display come-ups in increments of 10 yards, it showed the proper correction for that distance to be 35.25 MOA. With our original 38.25-MOA correction we were 3 MOA or about 33 inches high. Had we known the correct range to the target, the 4DOF-generated data would have allowed for an easy first or, since we had a bit of wind, second-round hit.

What makes all this possible is the math and mechanics behind the Hornady 4DOF ballistics calculator system. Its four degrees of freedom, taking into account windage, elevation, range, and angle of attack, allow trajectory solutions to be calculated with a drag coefficient instead of a ballistic coefficient (BC). It’s also the first publicly available ballistics calculator capable of determining the accurate vertical shift a bullet experiences as it encounters a crosswind, which is known as aerodynamic jump.

By using Doppler radar and actually shooting bullets, Hornady calculates the exact drag curve for every projectile in the 4DOF Bullet Library. (Currently there are more than 100 projectiles from Hornady, Lapua, Berger and Sierra.) BC can change as velocity changes, a drag curve doesn’t. Explained simply, instead of using BC, which gives you a snapshot of a bullet at various distances; Hornady has created a video of the bullet’s flight. This allows the 4DOF calculator to predict drop with perfection at any distance, every time.

The takeaway from all this — the one that’ll matter to you and your ammo — is that the Hornady 4DOF ballistic calculator is extraordinarily precise. Taking data this exact to the field on a first try is as rare as 17-year-old boys who can hit at 1,100 yards, six times in a row.

Check it out HERE

Download the app HERE for iOS

Download the app HERE for Android

RELOADERS CORNER: Bullet Jump, Three

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In this final installment you’ll learn how to take bullet jump completely out of the equation, but it’s not just that simple… Here’s how to get the results you’re after. Keep reading…

Glen Zediker

There’s one more concept to consider to fully finish the topic of bullet seating depth, and it’s literally on the other end of the equation from discussions on bullet jump.

Last two articles were all about a combination of the evils of jumping bullets and also some ideas on reducing the ill effects, and hopefully to the point of zero measurable group size differences. I also mentioned that there are some bullets that just don’t tolerate jumping.

JLK 105 VLD
Bullets like this tend (a true Davis-drawn VLD) not to shoot well unless they start right on or very near the lands. I sho don’t know for certain, but I really think it has at least some to do with, for want of a better way to describe it, their leverage: it’s a lot of front end ahead of the first point of land diameter. These really long bullets don’t have to tip much to shift alignment relatively more.

For many (many many) years it’s been generally held that starting a bullet touching the lands is the easy ticket to better accuracy. That’s hard to disprove. It’s a tactic very commonly used by Benchrest and Long Range Rifle competitors, and savvy long-shot hunters. Now we’re talking about zero jump. Myself and many others have referred to this bullet seating tactic as “dead-length” seating. To be clear: it’s the cartridge overall length that has the bullet nosecone actually sitting flush against the lands (touching on whichever point along the nose that coincides with land diameter). Some literally take that a step farther and increase contact force such that the bullet is sticking into the lands one or more (sometimes several more) thousandths, actually being engraved by the lands prior to launch.

There are two ways to attain or approach dead-length. One is through careful measurement using something like a Hornady LNL Overall Length Gage. That tool should be paired with a bullet-length comparator, and Hornady has one of those too, as do others.

Measure enough bullets using a bullet-length comparator and you will find length differences in a box of most any brand. A comparator, as has been shown before in my articles (because it’s a very valuable tool to increase handloading precision), provides a more accurate means to measure bullet length. It’s a simple tool: the bullet nosecone fits into the opening on the gage, stopping at a point (determined by tool dimension) along the nosecone. Not all such gages coincide with land diameters because both comparators and land diameters vary from maker to maker. They are all “close” but perfect coincidence doesn’t really matter because a comparator will allow a reading at the same point of diameter regardless. Measuring from the base of a bullet to the bullet tip is inaccurate, and not nearly “good enough” to provide a precise enough measurement to venture into lands-on seating depth experiments. The reason measuring from base to tip isn’t good enough is because, especially in hollowpoint match-style bullets, there are relatively huge variations in the consistencies of the tips. I’ve measured easy 0.020 differences in a box of 100. Can’t make bank on that.

Using the combination of the gage that shows overall cartridge length that has the bullet touching the lands and the comparator to precisely record this length, it can then be reproduced via seating die adjustment.

Hornady LNL gage setHere’s a tool set shown many times in my books and articles this pair or something similar is necessary to negotiate this step in handloading. Check it out HERE and HERE at Midsouth.

If using this method, maintain whatever usual neck sizing dimensions are for your routine loads. There’s no need or benefit from lessening the case neck “tension” (which is the amount, in thousandths of inches, of the difference between resized case neck outside diameter and the resulting diameter after a bullet is seated). If that’s, say, 0.003 then keep it at 0.003.

There’s another, maybe better, method to follow if (and only if) you have a bolt-gun that’s to be fed one round at a time. By that I mean the rounds are not feeding up from a magazine but are being manually inserted into the chamber. That method is to reduce the case neck tension or grip to a level that the bullet is free enough to move within the case neck such that it seats itself when the round is chambered and the bullet makes contact with the lands. That’s awfully light in-neck resistance. It can’t be so light that the bullet falls into the case neck, but light enough that it can be scooted more deeply with little pressure. For a number it’s 0.001, minus, and half of that is workable if the case necks have been outside turned (so they are dead consistent in wall thicknesses and therefore will reliably “take” that little tension, meaning respond consistently to the sizing operation). Need a bushing-style sizing die to get that sort of control over the neck sizing dimension.

This method is often called “soft seating.” It’s, as said, very popular with competitive precision shooters. The bullet, keep in mind, isn’t just touching the lands, it’s actually engaging the lands to whichever degree or distance that resulted from overcoming the resistance from the case neck. If you feel anything more than slight resistance in chambering a round, that’s too much resistance. Chances are that any soft-seated bullet will stick in the barrel so extracting a loaded round will likely result in a big mess (elevate the barrel a little to keep the propellant from dumping into the action). Pushing the lodged bullet back out and looking at it carefully gives a good idea of how much resistance it’s overcoming. If the engraved area is much over 1/16-inch, increase the neck sizing bushing diameter to likewise loosen up the case neck. The amount of engraving has a whopping lot to do with the bullet jacket material (you’ll see more with a J4 than with a Sierra).

If you follow this method, then finish the die-seated bullets “out” 0.005-0.010 inches.

Redding sizing die bushing
It’s necessary to be able to fine-tune neck sizing dimension to experiment with soft-seating. A bushing-style sizing die is best. The bushing might also change for different brands or lots of brass if there are thicker or thinner neck walls. Clearly, outside neck turning is a step toward consistency in this sizing operation.

The reason this method can give the overall best results is because it’s accounting for teeny differences in bullet ogives and it also is adjusting itself for throat erosion. As gone on about in the last couple of articles, a barrel throat is lengthening with each round that passes through. What was touching the lands, or jumping 0.015, even one hundred rounds ago is no longer valid, and it’s totally corrupt five or six hundred rounds later. It’s no longer a precise setting, meaning a precise seating depth, and it has to be checked and reset as the barrel ages.

Again, this is not a casual experiment. The level of control and precision necessary to make it work safely and as expected is a step or three beyond what most reloaders are tooled up to deliver.

Will lands-on seating work for a semi-auto? Yes. But only with adequate bullet grip to retain the bullet firmly in the case neck, and that means the same tension that would be used with any other cartridge architecture, and that means a minimum of 0.003 inches difference between sized and seated outside case neck diameters. I do it often with my across-the-course High Power Rifle race guns. Clearly the “soft-seating” tactic is in no way wisely feasible in a semi-auto.

WARNING!
MOVING A BULLET OUT SO IT TOUCHES THE LANDS WILL (not can) INCREASE LOAD PRESSURE! Even going from 0.001 off to flush on will spike pressure. When the bullet is in full contact it’s acting like a plug. I strongly suggest backing off one full grain (1.0 grain) before firing a bullet touching the lands. Then follow my “rule”: work up 0.2-grains at a time but come off 0.5-grains at a time! If there’s ever any (any) pressure symptom noted, don’t just back of a tenth or two, that’s not enough, not considering all the other little variations and variables that combine to influence the behavior of the next several rounds you’ll fire.

THREE REASONS DEAD-LENGTH SEATING WORKS
ONE: Accounts for and overcomes any minor variations in bullet dimensions.
TWO: Minimizes bullet jacket disruption on entry.
THREE: Virtually eliminates misalignment between bullet and bore.

SIDE NOTE
If you’re one who, as many readers have suggested to me, has found that seating a bullet to touch the lands is the only way they get good groups, consider the above three reasons this seating method works and then interpret. If, and this is more common than we’d like to see, you’ve got a factory bolt-action rifle the chamber is likely to be overly generous in size or a tad amount non-concentric, or both. The case wall consistency and also sizing and seating tooling, or all three, might likewise be sub-par. In other words: lands-on seating is overcoming a few rifle issues, not, in itself, proving it’s the one-way ticket to great groups. Mostly, getting the bullet into the lands essentially straightens out alignment of the whole cartridge sitting in that (maybe) big chamber.

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.

RELOADERS CORNER: SD Pt. 2

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Here’s how to use (or not use) Standard Deviation calculations in ammo decisions, what they are, and aren’t… Keep reading…

Glen Zediker

A standard deviation plotted out is a bell curve. Chances are outstanding that a range session calculation will plot into what they call a “normal curve.” Like any normal bell curve, it can get divided into three segments and given values, and, technically, these are the “standard deviations.” It’s “a” standard deviation rather than “the” standard deviation.

SD bell curve plot

Assuming a normal curve, the values are that about 68 percent of forecasted results will lie within one standard deviation of the mean, about 95 percent lie within two, and over 99 percent lie within three standard deviations. If we have an SD calculated to be 12, that means that applying one standard deviation means that about 68 percent of all “next shots” will be +/- 12 feet per second. Since, though, the curve is in threes, in effect if not in fact, that means that a scant number of the shots pose a chance for +/- 24 and some teeny chance remains for shots to go to +/- 36. That, however, is extrapolating or predicting with data and that’s not really wise and doubtlessly uncalled for. Data collection is a record of numbers and I do know that there’s 100 percent chance that the highest and lowest velocities collected for an SD calculation did, in fact, happen. That’s what matters. No matter what the shot results calculated into for an SD, those were the two that represent the highest and lowest prints on the target.

It’s mathematically not possible for an SD to be higher than the greatest single raw deviant, but I do for a fact know that an SD can easily be far lower than the worst shot. Given how it’s calculated, along with how many samples contributed, it’s plain that the nearer the majority are to themselves the less impact a bad one or more has.

I said in a very open-ended way last article that a tolerable SD is 12. Anything more than that is not good; anything less than that probably won’t perform noticeably any, if at all, better than a 12. However! It is at this number, so I say, where the often-uttered tune of “…SD doesn’t matter…” and its refrain of “…seen good accuracy with high SDs…” starts and stops. Twelve. That’s it. Now we have an SD that “doesn’t matter.” The reason this is stuck out here is that everyone has heard this chorus but hopefully figured that it couldn’t be taken universally at literal value. Well it can’t.  So now you know! It’s 12. 12 should not be responsible for a points loss, even accounting for or including coincidence of any one shot hitting the edge limit of usual group size.

(Yes, 13 or 14 or 16 or even 20, which is often given as a “limit,” might well be a realistic ceiling but I drew a line to have one. Since there’s a line, now we can cross it and commence argument. I won’t use any load in competition that wouldn’t calculate to a single-digit SD. My 600-yard .223 Rem. load tested to an SD of 3.18 with a Range of 8 fps.)

So after all this has been said, I don’t give SD as much weight in my load decisions as some do. The reason for my focus on it here, as said in the first article, is because that’s the usual “standard” measure of consistency. I look at the speeds as they come up on the chronograph display and write them down. I weigh range and extreme spread more heavily, and I want to see really small variations over the number of test rounds I fire. It’s a matter of waning patience and waxing time. If I see a variance that could cost a point, that load is abandoned.

TESTING TIP
If you don’t have a chronograph or don’t want to burden a testing session with using one, watch for a correlation between the elevation dispersion and the wind dispersion of test groups. At 600 yards I always test from position (prone, “suited up”). No chronograph (muzzle-mounted chronographs now make this a non-issue). I’ll already have speed-checked the load I’m now down on the mat with. When I shoot my groups, I honestly don’t pay much attention at all to anything but measuring how level I got my perforations. Attempting shot-to-shot wind corrections when testing for ammunition accuracy throws another variable into it that might be most misleading. If I come up with a group that’s a foot wide but only three inches tall, I’m happy.

5 TIPS FOR LOWER SDs
Aside from finding the perfect and magical load combination, ha, there are a few things that do seem to help tighten shot-to-shot velocity deviations. They’ve all be talked all the way through and back again in this space in other articles, but, considered ultimately that this is the overall effect they have, here they are again:

One. Primer seating: fully seated onto a flat pocket bottom.

Two. Consistent propellant charge: weigh the charges if metering isn’t dead-on perfect.

Three. Ignition efficiency: consider that inside flash hole deburring routine…

Four. Temperature insensitivity: choose propellants that exhibit stability under extremes.

Five. Balance: strive to find a propellant that fills the case, but “loosely” (no compressed charges); even more, avoid an overage of air space. These both allow too much variance in ignition pattern.

Propellant level.

Addition
I learn things all the time. A most knowledgeable and helpful reader pointed out a detail in SD calculation that is better adapted to calculations for ballistics, and it helps because of the usually relatively small size sample involved. We’re not going to chronograph 100s of rounds, usually 10-20. So, instead of dividing the average square of the deviations by the number of samples, but the average square of the values, less one (n-1). That helps any distortion of results toward a number that calculates too small. Keep in mind always that SD is an estimate, in one way of looking at it.

This article is adapted from Glen’s book, Handloading For Competition, available at Midsouth HERE. For more information on that and other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: SD — what it matters and why

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Getting a handle on improving long-range accuracy has a lot of to do with understanding the importance of consistent bullet velocities. Here’s a start toward that…

Glen Zediker

There’s one more thing (seemingly, there’s always one more thing…) that’s important to accuracy at extended distance. I’ll say “extended distance” is anything over 300 yards. That is bullet velocity consistency.

I’ve said in these pages before that a good shooter will lose more points to elevation than to wind. This next explains that a might more.

First, and the first step, is getting and using a chronograph. It doesn’t have to be a zoot-capri model, and nowadays that’s a fortunate bonus because there are a number of inexpensive chronographs available that are entirely accurate.

PACT chronograph.
A chronograph is essential, well, at least for all this here. There are a lot of good ones. I’m partial to PACT.

Check Misdouth offerings HERE

magnetospeed chronograph
The newer barrel-mounted electro-magnetic chronographs make it really easy. I like the idea of being able to chronograph from shooting position, not just from a benchrest. This is a MagnetoSpeed.

“Standard deviation” (SD) is probably the most commonly used measure of bullet velocity consistency. SD reflects on the consistency of velocity readings taken over a number of shots. “Standard” reflects on a sort of an average of the rounds tested.

[Math folks don’t use phrases like “sort of” when describing numbers and can provide tickier definitions of SD and the means to calculate it. Here it is: it’s the square root of the mean of the squares of the deviations. Actually harder to say than it is to calculate.]

Steady Wins the Race
Standard deviation is not the only measure, and I don’t even think it’s the right one, let alone the most important, but it’s no doubt the most popular way to talk about ballistically consistent bullet performance. I don’t think standard deviation is near as important as is the “range,” which is the lowest and highest speeds recorded. Some who write and talk about it call that “extreme spread,” but if we want to get picky over terms (and ballisticians, card-carrying and self-styled, tend to get right touchy over such formalities) extreme spread is the difference between this shot and the next shot.

I watch the speed on every shot. I compare this one to the next one and to the last one, and, as said, find the highest and the lowest.

There is no saying that a load that exhibits low standard deviation is going to group small, just because of that. Any Benchrest competitor will tell of experiences whereby “screamer” groups came with high SDs and hideous groups with low SDs (“high” and “hideous” by their standards, still pretty small for the most of us). But, at 100 yards the bullet’s time of flight and speed loss are both so relatively small that variation in bullet velocities isn’t going to harm a group, and, yes, not even the tiny groups it takes to be competitive in that sport. On downrange, though, there is going to be a relatively greater effect on shot placement, right? Yes and no. Drift and drop are influenced. There is a relatively greater effect in ultimate displacement of elevation, more next. Based on drift allowance it probably does not.

To put an example on it, let’s say we’re shooting a Sierra® 190gr .308 MatchKing. Its 2600 fps muzzle velocity becomes 2450 at 100 yards and 1750 at 600 yards. (All these numbers are rounded examples, and examples only.)

If we’re working with a truly hideous inconsistency of 100 fps, say, that means one bullet goes out at 2550 and the next leaves at 2650 in a worst-case event. The first bullet tracks across about 28 inches (constant full-value 10-mph wind to keep it simple) and the next moves sideways 26 inches. Figuring drift on 2600 fps means it’s two inches off, one inch per shot.

Drop, which means elevation, is a (the) factor, and here’s where poor SDs bite. With this Sierra® 190, drop amounts over a 100 fps range are about three times as great as drift amounts. A vertically-centered bullet at 2600 fps hits about 5-6 inches higher or lower at each 50 fps muzzle velocity difference. That’s enough to blow up a score to elevation. And it gets way, way on worse at 1000. Keep always in mind that velocity-induced errors are compounding “normal” group dispersion. And, in reality and as discussed before, it’s unusual in a competitive shooting venue for a wind to be full-value, so the on-target lateral displacement is even relatively less — but the elevation displacement is consistent.

The next-to-the-bottom line, then, is that poor SDs don’t hurt in the wind as much as they do on the elevation. The bottom-line, then, is back to the start: don’t shoot a load with inconsistent speeds. It’s flat not (ever) necessary.

So what’s a tolerable SD? 12. That’s the SD that “doesn’t matter” to accuracy. More later…

SD bell curve
Standard deviation calculation forms a bell curve. The steeper and narrower the apex of the bell, the more level and narrower the fluctuations were. But there’s always a bell to a bell curve and the greatest deviations from desired standard are reflected in this portion of the plot. Depending on the number of shots that went into the SD calculation, these deviations may be more or less notable than the SD figure suggests. So? Watch each shot. That’s the way to know how a load performs with respect to velocity consistency. Each and every speed collected for each and every shot fired in a test. More next time…

MATH: For Them That Wants It
If you have no electronic gadgetry to help, calculate SD like so: add all the velocities recorded together and divide them by however many there were to get a mean. Subtract that mean number from each single velocity recorded to get a deviation from the mean. Square each of those (eliminates the negative numbers that ultimately would cancel out and return a “0”). Add the squares together and find the mean of the squares by dividing again by the number of numbers. Then find the square root of that and that’s the standard deviation figure, which is “a” standard deviation, by the way.

This article is adapted from Glen’s book, Handloading For Competition, available at Midsouth HERE. For more information on that and other books by Glen, visit ZedikerPublishing.com

 

 

REVIEW: Savage Arms BA10 Stealth 6.5 Creedmoor

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If you’re in need of an out-of-the-box long-range tack driver, and don’t want to pay thousands, this Savage proved a great choice in this test. Read more…

by Patrick E. Kelley

Savage Stealth BA10

The Savage Arms BA10 “Stealth” is anything but stealthy! This rifle shows up “in your face” ready to put bullets in little groups up close, or where the real test is — way out there!

CUTTING TO THE CHASE…
Lets start at about “half way” to way out there. This AICS (Accuracy International Chassis System) compatible box magazine-fed turn-bolt is accurate! While many may claim half-minute accuracy, this stick actually is that precise, and it can do it right out of the box. Take a look…

Savage Stealth 450 yard groups

Now I would love to take credit for those groups, but knowing my longer-range skill set was less than what I expected the rifle could shoot, I enlisted the help of my shooting buddy Bill. As an F-Class competitor, he knows his way around long range shooting. It took a few shots to get him settled in behind this rather lightweight (9.2 pounds) long range bullet placement tool, but settle in he did. Yes, I included ALL 5 groups! We got to take the good with the bad, but I would ask you to really look at those groups…this rifle wants to shoot 1/2 MOA or better! Thanks Bill!

benchrest setup
This was Bill’s set up. A good shooting rest setup is very important to good groups.

SET-UP
With the Savage carrying a MSRP of $1207 I thought it would be a good idea to marry this rifle up with a comparable scope. I chose one that, like the Stealth itself, has value well beyond its modest price: the Burris XTRII 5×25. I tell people, “Don’t buy cheap scopes!” Buy good glass and then put them in the best mounts. You will break a scope someday, but a good mount will last though several scopes! The scope base is part of the Savage BA10 package and is made by the good guys at EGW, and the scope rings I supplied are 34mm units from Xtreme Hardcore Gear. “On right stays tight” — use a proper inch-pound torque wrench!

Savage Stealth, Burris scope

HITS
This bolt gun’s “chassis system” is made by MTD and is a solid, well-made unit. I popped the barreled action out of the stock before the first rounds went downrange and looked it over. It is very nice and beautifully machined. I mentioned using an inch-pound torque wrench for scope mounting, well it is a good practice to use one when installing the barreled action back into the chassis. I did 60 inch-pounds.

Savage Accutrigger
Savage has really put their AccuTrigger front and center as a high quality unit and this one did not disappoint! It broke clean and crisp at a factory-set 22 ounces! In keeping with the “practical/tactical” nature of this bolt gun you’ll find an appropriately over-sized bolt handle, a comfortable Hogue pistol grip from which to trip that excellent trigger, and quick access to the magazine release latch. The excellent ergos on this rifle were no accident.
AICS magazines
Above are the 3 magazines I tested…all worked perfectly. The tall one on the left came with the gun as is an MDT 10-rounder. The other two are 5-round mags from MagPul, and are AICS compatible.
threaded muzzle cap
The muzzle is threaded 5/8x24tpi and finished with an 11-degree target crown and thread protector: a handy addition to accommodate a suppressor or muzzle brake.

I could not just watch my friend Bill shoot so after he completed his session with the Hornady factory ammunition at 450 yards I tried my hand at 300 yards with some Federal American Eagle 140 grain OTM (Open Top Match). Even with me behind the incredibly nice 22-ounce Savage AccuTrigger, sub-minute of angle groups were the norm. Norm…that is not normal! Sub-MOA groups from a factory-fresh rifle without any tuning or tweaking or even barrel break-in with off-the-shelf factory ammo! I think I am going to like this long-range game! Thanks Savage!

300 yard groups

MISSES
We covered most of this, but let me point out a nit-pick or two. You knew I would have at least one… The EGW scope rail appears to be a “flat” rail, not a 20 or 30 MOA rail that is common in long-range circles. If you have enough elevation adjustment within your optic you might be okay, but give me a 20 MOA base any day.

Then there’s the buttstock… I don’t like it. It is okay for an AR but this one lacks two elements that I want (need): first, the cheek rest sits too far back to get proper eye relief, and second, for use with a rear bag the bottom of the buttstock ought to be flat. Small nits to pick, and both are easily remedied through the aftermarket.

LAST WORD
The BA10 Stealth has proven itself to be accurate and reliable with a trigger that has me wishing every rifle I own were so equipped! It does this “right out of the box” and it does it within the wallet of a “working man.” Ultimately, Savage Arms has assembled an excellent long-range tool that in capable hands shouldn’t have any problem running right along side guns with price tags several times the Stealth price. Stealthy?…not a chance. This one screams “I am a winner!”

Savage Stealth Specifications
So as to not leave anything out, Savage literature states: Factory Blue Printed Savage Action, Monolithic Aluminum Chassis Machined from Solid Billet, M-LOK forend, One-Piece EGW Scope Rail, Fab Defense GLR-SHOCK Six-Position Buttstock with Adjustable Cheek Piece, 5/8×24 Threaded Muzzle with Protector. Nice!

Click here for MORE information on the Savage Stealth series

About the author: Patrick E. Kelley is a competition shooter, instructor, gunwriter, photographer, and videographer. After four years as a featured competitor on 3-Gun Nation he was hired as the Expert Analyst and commentator for the show. He started to compete actively in 3-Gun in 1999, placing Top Tyro in his first championship, the Soldier of Fortune 3 gun match. Patrick has earned numerous first-place finishes at major matches in 12 U.S. states and Canadian provinces. He has mastered several shooting disciplines, from NRA Bullseye and Metallic Silhouette to the world of Practical Shooting. Patrick is also a member of the NRA 2600 Club and was ranked in the USPSA’s top twenty early in his shooting career. Patrick’s articles on shooting and firearms, as well as his photography, can be found within the pages of Shooting Illustrated, Outdoor Life, and 3 Gun Nation Magazine. His YouTube channel includes instructional and exhibition shooting videos, including the series “Patrick’s Tac Tricks” produced in concert with the NRA. Check one out HERE

 

Shooting Skills: Shooting The Breeze, 3

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Putting it together: follow these suggestions and lose your fear of the wind!

Glen Zediker

Up to here we’ve talked over the influential factors wind brings with it. Here’s how to take it right back to the wind.

First, there are two essential “types” of shooters with respect to how they adjust for the wind on each shot. Dopers and chasers. I’m a chaser. A doper, wind doper, is one who carefully studies inputs and makes what amounts to a unique correction for each round fired. I say unique because it takes more time. They constantly evaluate and calculate the influence and often do much of it using one of the hand-held wind-meters talked about earlier.

I’m a “spotter-chaser,” which is actually a tad amount demeaning term branded on my style by the dopers. Technically I’m not really “chasing the spotter,” which means adjusting based solely on the position of the last shot. No. I’m anticipating a needed change based on observation between shots, but I’m doing it quickly, and I use the spotter location to confirm or modify my setting. That tells me if I’m seeing what I think I’m seeing. (A spotter is an easily-visible disk on a spindle that’s inserted into the location of the last shot hole by the folks pulling targets in the pits.)

Remember what was said last time about wind cycles? Usually there’s between 6-8 minutes before a cycle repeats, a little more or a little less. I want to get all my rounds downrange, if target pit service allows, during one cycle. Shooting into a build-up, watch for indications of a wind velocity increase. If the wind is moving left to right, I don’t want to see anything too close to the right edge of the 10-ring; I hedge a half-minute of angle or so to guard against losing a shot that direction if there’s an increase I missed, but not hedging so much that I’ll be too close to the left edge if I misread and overcorrect for a pick-up.

Pick one indicator, stay with it.

David Tubb
Most good shooters use mirage as their leading indicator to spot changes in the wind. With well-designed stand, the scope can be set it up where you can see the wind with the left eye and see the sight with the right without anything more than a visual focus shift. That gets the shooter back on the trigger with the least chance of missing another change. David Tubb demonstrates.

There are resources that give clues or evidence of wind direction and strength: wind flags, observation of grass and trees, and mirage.

Almost always I use mirage as my leading indicator. Mirage (heat waves) is always present but you’ll need a scope to read it. For 600 yards I focus my scope about halfway to the target. Mirage flows just like water and the currents can be read with respect to wind speed as well, but it’s not clearly accurate beyond maybe a 15 mph speed. The thing is that mirage shows changes, increases or decreases, and also direction shifts, really well.

A couple more things about mirage flow: when mirage “boils,” that is appears to rise straight up, either there’s no wind or the scope is dead in-line with wind direction. And that’s a quick and accurate means to determine wind direction, by the way, move the scope until you see the boil and note the scope body angle. It’s also how to know when a “fishtail” wind is about to change, a boil precedes a shift.

I use a long-eye-relief 20X to 25X wide-angle eyepiece. That setup shows the flow best. And pay attention to where the wind is coming from! See what’s headed your way, because what’s passed no longer matters. That’s true for any indicator. Right to left wind? Read off the right side of the range.

wind zero
Shooting into and through a buildup is a good strategy. My plan is to hedge against losing a shot “out” so I normally have an “insurance click” on to guard against missing an increase in wind value, and also hoping a sudden decrease doesn’t bite me and land one inside the wind. 10s win. Clearly, being able to honestly and precisely call a shot is a huge asset. That’s the only way to get good feedback from the last shot location.

Once I get on target then all I am doing is watching for changes. It’s really uncommon to make a big adjustment between shots. Once a string starts it’s ones and twos, back and forth. The fewer condition changes you are enduring, the easier it is to keep everything on center. That’s why I shoot fast, and that’s why I start at the low point in a wind cycle.

Speaking of getting on target. If it’s an NRA High Power Rifle event, you’ll get two sighters. I put my best-guess correction on before the first sighter, plus two clicks extra into the wind. Example: it’s quartering left to right and I’m guessing 2MOA, so that’s 8 clicks in the “left” direction, so I put on 10. That’s how I find out if I saw what I thought I saw. Then, and this is very important: Make a full correction off the result of that first sighter! Put the clicks on that would have centered that shot. The exception is if there was a notable change sensed between the first and second, but, even so, first sighting shot location lets you know if you got the value (what the wind is worth) under control. There’s one more round to go before you’re on record, so interpret from that and start the string.

sighter correction
Make a full correction off the first sighting shot location! Even if there are minor changes afoot, that’s how to know how well you assessed condition influence pre-shot. Don’t second-guess. After the second sighter you should be on target and then simply watching for changes. Pay attention, correlate visible cues to the results of prior shots, and if in doubt, click into the wind.

If you’re not at an organized event, having a spotter helps! Getting someone to watch for impacts while you shoot is a huge time-saver.

Information in this article was adapted from material in several books published by Glen Zediker and Zediker Publishing. Glen is a card-carrying NRA High Master and earned that classification in NRA High Power Rifle using an AR15 Service Rifle. For more information and articles available for download visit ZedikerPubllishing.com

Shooting Skills: Shooting the Breeze, 2

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Adjusting for wind effect first comes from collecting information. There are two main components and one very important key. These three steps are essential. Keep reading to learn more.


Glen D. Zediker


Learning to shoot well on a windy day involves inputs. A lot of inputs.

Pretty much: wind speed and wind direction are the combining key factors that determine how much sight correction or “hold off” (if you prefer) is needed to get to target center. Speed and direction inputs combine to make a decision on the correction amount. Speed and direction, in tandem, have compounding or offsetting influences on the amount of correction. If either changes, the correction changes.

For instance: if the direction changes and the speed stays the same or the speed changes and the direction stays the same, it’s just more or less correction. But it’s imperative to keep in mind that these are linked.

Most shooting ranges, if construction plans made it reasonably feasible, are set up facing North. That helps. Head- and tail-wind components are less influential than the cross-wind component.

1. Estimate Speed
Being a competitive shooter and, therefore, an admittedly unashamed gamesman, employing some sort of short-cut electronic trickery comes first to mind. A wind meter is the fastest and surest way to get a start on a number. There are very good hand-held meters available, and these range in cost, convenience, and complexity levels. Some provide vauable additional information (such as density altitude), the use of which will be talked on another time.

wind meter
Learning to read wind speed comes only from experience, but something like one of these Caldwell-brand units jumps the learning curve way on up in a hurry. It’s simple, accurate, and well worth the less than $100 it costs. This is the Cross Wind Professional Wind Meter. See more HERE.

Visible indicators are simply observations. If it’s a shooting range, and if there are wind flags, look at the angle the wind is standing a flag out to, divide that by 4 and that’s a close approximation of wind speed. Of course, that depends on the flag material, and so on. Wind flags mostly help sense direction.

I know this is a serious cop-out, but experience is really the only teacher. There’s an old-school wind estimation guide first published eons ago that provides some input on guessing wind strength based on environmental clues. Click HERE to download an updated copy of the “Beaufort Scale.”

Stop! The wind doesn’t always blow the same the entire span of the range. Especially in the West, it’s plenty common to see faster or slower velocity areas between the firing line and the targets. Trees, ground clutter, topography, and so on, all create either passages or obstructions to the flow of the wind. Up to 600 yards, wind nearer the shooter should be given more weight; beyond that distance, wind strength nearer the targets is likely to exert disproportionate influence on the bullet. Reason is a matter of bullet velocity at the point of more or less wind impact. To be clear: even if we’re seeing relatively calm conditions at, say 500 yards, but it’s a tad amount gusty up close to the muzzle, early deflection of the bullet compounds to exert a stronger influence the farther the bullet travels.

range wind speed
Wind doesn’t always blow the same across the full depth and breadth of the range. Up to 500-600 yards, give a little more weight to the wind behavior (speed mostly) nearer the firing line. And, keep in mind that you’re shooting down a one-target-width corridor! Pay attention where it matters.

2. Determine Direction
This should be easy. However! Direction can change just as can speed. It’s not normally going to swap, but rather will vary in fractional shifts. A ticklish wind is a “fishtail” that waffles between 11 and 1 o’clock.

range flag
If there are flags on your shooting range, they mostly function to indicate wind direction, but can be a clue to wind speed: divide the angle by 4 and get an approximation of speed in miles per hour. Call this one 18 mph.

3. Find The Pattern
This may be the most important advice I can give on wind shooting. Wind cycles. Rarely does it blow at a constant and steady rate for very long. Wind cycles every 5-10 minutes. It builds, then peaks, then drops, then as implied, it runs the cycle again. That doesn’t necessarily mean it goes from calm to windy; it goes from windy to windier. But it will change, and most often will do so predictably. Watch the wind for a spell, running a stopwatch, and make notes on what you’re estimating for values at the high and low in the cycle.

At a tournament I want to shoot into a build-up, or, in other words, start my string at the low point in the cycle. And I also want to shoot all my rounds within the timeframe of the cycle! We have 20 minutes at the 600-yard-line, so scheduling can be an important part of strategy for this yard-line.

wind cycle
The most important thing I can tell you about wind: It cycles! Pay attention before you shoot and time the highs and lows you see. Chances are this pattern will repeat over and over at least for the next hour or so. This knowledge is also a huge help to varmint hunters.

If you know what amount a 10-mile-per-hour crosswind will (is supposed to) move your bullet at some distance, interpret the initial correction from that. If you guess the wind at 5 mph, take half of it; if the angle is less than full-value, reduce the correction as discussed last time by the fractional value, like half of the estimated amount for a wind that’s moving from 4:30 to 10:30.

clock face
For reference…

None of this is finite. Reading wind is more art than science. Next time I’ll talk about how to put all the inputs to use and keep all your shots on target.


Information in this article was adapted from material in several books published by Glen Zediker and Zediker Publishing. Glen is a card-carrying NRA High Master and earned that classification in NRA High Power Rifle using an AR15 Service Rifle. For more information and articles available for download visit ZedikerPubllishing.com

Shooting Skills: Shooting the Breeze

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Longer-range rifle shooting isn’t easy, and it’s more difficult when the wind is blowing. Here’s a head start on learning to determine and correct for environmental conditions.


Glen D. Zediker


When I very first started up working with Midsouth, I had quite a few folks writing and requesting to learn more about shooting, and, specifically, NRA High Power Rifle competition. It did my heart good to learn that these folks knew my name and associated it with that venue. HPR has been the main focus of my shooting career. That background is the reason I began the “Shooting Skills” portion of the newsletter, and for a few installments upcoming I will oblige to further go a little deeper.

Wind.

That’s one of the first things that comes to anyone’s mind when High Power is the topic. Describe the tournament course of fire and when you get to “…then 20 rounds at 600 yards…” that one creates a tad amount of anxiety in the imagination.

600 yard shooting
t’s a big, wide, windy world out there. There are several influential factors beyond wind speed and direction, and this series will piece them all together to provide a picture of how to anticipate wind effect on your bullet.

First comment is almost always, “How do you shoot that far with iron sights?” And that’s easy: the target is huge! The aiming black or bullseye is scaled up to a diameter that provides a clear reference to position the sight. And then the next is, “What about the wind…” Well. First, it’s really not that difficult. Second, it’s also really not that easy. You need to know a few things, so here’s where we’ll start.

To be sure, organized competition is not the only venue where learning to shoot in the wind helps. It’s a skill that anyone who fires across more than 200 yards worth of real estate needs to develop. It’s a little easier in a shooting contest because there’s some feedback to work with: holes in the target.

There are two influential components to wind, and, “influential” means the effect on moving the bullet. Speed + Direction. There are good ballistic programs and apps now that provide approximate values: input the points (bullet ballistic coefficient and wind speed) and get a fast answer. That answer is liable to be incomplete, and by that I mean it’s rare indeed to dial in the given solution and hit the target. One at a time we’ll look at other factors which, taken all together, will get you a whole lot closer on that first shot.

The better apps allow also for angular extrapolation, and that is important. Otherwise, if you’re looking at a table the drift amount will be for a “full-value” wind, which is blowing at a right angle or perpendicular to the rifle barrel. Straight crosswind, 9-o’clock to 3-o’clock, or vice versa. If there’s an angle involved, reduce the amount of anticipated drift based directly on the angle: if the wind is angling from, say, 8-o’clock to 2-o’clock we’d say that was a “half value.” From 7-o’clock to 1-o’clock that’s closer to a “quarter value.” So if the drift table says 12 inches, half is 6 and a quarter is 3. At 600 yards it doesn’t really matter if the wind is coming in or going out: head- or tail-winds have little unique influence on the bullet.

And speaking of, there is a different set of “rules” for 1000 yards and more, or maybe I should say different applications or emphases. The reason is because the bullet has slowed down that much more.

At minimum you’ll need to know the advertised BC or ballistic coefficient of your bullet and its muzzle velocity. I wish I didn’t have to continually offer up all the “maybes” and qualifications, but I do because they exist. The actual realized or demonstrated BC of any bullet varies day to day, often during the day. Velocites can also change a bit for varied reasons. However! None of this honestly really matters to the score and that is because the combination of BC and velocity just gets us “close” and finds a place to start from. Ballistics is a finite science, but there are no finite results. With experience you’ll see that BC is really mostly a way to compare different bullets; its value in making truly accurate and finite corrections is limited.

David Tubb 115 RBT 6mm
High-BC profiles are a big bonus, but there’s no magic bullet. The reason better bullets are better is not because there will be less correction on the sight. That doesn’t really matter all that much. Why they are better is because they are less affected by an immediate and perhaps unforeseen change in the wind stats. They are deflected less by, say, a 1 mile-per-hour shift. Shown is a 115 RBT 6mm developed by David Tubb. It’s slick…

All this is affected by air density and that’s a whole other topic for a whole other time. And there’s another list of inputs that each have an influence, and that, again, is why this little series is a series.

Dang. There’s a lot to talk about and I’m pretty much out of space. That’s what “next times” are for. I’ll keep this going long enough to provide some genuine help.

Understand that arriving at a sight solution that keeps the shots in the center involves more input that any “drift/drop” equation can provide.


Information in this article was adapted from material in several books published by Zediker Publishing. Glen Zediker has worked professionally with some of the greatest shooters on the planet, and he does pretty well on his own: Glen is a card-carrying NRA High Master and earned that classification in NRA High Power Rifle using an AR15 Service Rifle. For more information, please check ZedikerPublishing.com