montea6b,

read the entire post if you would please.

I did not mention it, but all of my data was derived from an Oehler 35P chronograph. It measures the MV twice.

Per your thoughtful question, Ken told me, when I attended his chronograph school and got my 35P; that their design tolerance was about +/- 3fps with the standard 35. The P in 35P stands for Proof, and it cuts that to slightly less than half of the 35. That by comparing the two MV numbers. I drove down to Austin for the school, so I got to see how his pressure testing unit worked as well, and brought a unit home. Along with the 35P. It is a comparative type of analysis, not an absolute one. Absolute involves destruction testing, and most of us cannot afford a railgun and disposable barrels.

Back on task: I just want someone to tell me, in layman's terms, what SD is, and how the number is arrived at.

I did read the whole post. I wasn't accusing any one individual with my comment, and it is an observation that applies to a lot of threads. But, since you threw out the term "jackass braying" would you say the shoe fits?

I have a layman's understanding of SD from taking a work related six sigma class years ago, but I probably cannot offer a simple explanation that will help the light come on for you. I often turn to Wikipedia for these sorts of things: Standard Deviation

I'm a picture guy, a smaller SD means the bell curve will be narrower, a large SD will spread the curve out. SD is just a number that states the percentage appearing within a certain distance from the mean. (not sure how it is actually calculated or how the formula was derived)

Sort of... I think...

Not sure if that helps or not.

P.S. Thanks for the info on your chronograph's tolerance. Good to know...

thank you, it does.

As far as the "jackass braying" I plead guilty as charged. The person in question and I have issues. IMHO, he considers himself somewhat above the crowd. But, you will note, that his post did not add anything to the discussion as far as explaining SD; just a cheap shot at me.

My biggest failing is a very low tolerance for inane-ity.

thanks again,

Rich

I don't worry about single digit standard deviations until I start shooting past 400 yards. At 400 yards using normal velocities, a variation of 100 fps will result in a trajectory change of less than 2" (.264 SMK). Which, if you are zeroed correctly would result in every bullet impacting within 1" of the group center.

At 1,000 yards the same 100 fps variation would result in a 16" group, in a perfect world.

I was out shooting LR today with a variety of calibers (8 total) and - using the new LabRadar - I got a range of SDs from 6 to 22 (mean 11.4). The 338 RUM SD was 6 while the 22-250 had a SD of 12.7 and 22 - two different loads for the 22-250. Yet, I was hammering the steel targets at 635 yds with the 22-250 using 55 gr NBTs.

I don't anneal, but I try to keep all else very tight.

From a recent article on the effect of muzzle velocity SD on hit probability using WEZ analysis, I've learned that dropping SD below 10 down to 5 only increases hit probability by less than 1%. IMO that 1% is not worth the additional effort.

See...

http://precisionrifleblog.com/...much-does-sd-matter/

I remain unconvinced that annealing is worth the effort.

Any comments?

Regards, AIU

This is a summary article on a number of aspects of LR shooting...

http://precisionrifleblog.com/...ter-overall-summary/

How Much Does SD Matter?

As long-range shooters, we tend to obsess over every little detail. After all, we’re trying to hit relatively small targets that are so far you may not even be able to see with the naked eye. While you might can get away with minor mistakes and still ring steel at short and medium ranges, as you extend the range those small mistakes or tiny inconsistencies are magnified. So, most things are important … but to differing degrees.

There are so many variables that it’s easy to get lost, and most of us end up doing our best to spread our finite energy and resources in every direction. Is there a data-driven approach to help guide us toward the most important factors to increased hits at long-range?

I’m glad you asked! Bryan Litz created the WEZ (Weapon Employment Zone) analysis tool to gain some insight into this dilemma. So I dropped $200 for the Applied Ballistics Analytics Software Package, which allows you to run your own WEZ analysis. This gives you the ability to systematically study how different field variables in real-world shooting affect the probability of hitting long-range targets. Here is his summary of this software package:

“The Applied Ballistics Analytics software tool is a full-featured ballistics solver that includes the capability to compute expected probability of hit using the same Weapon Employment Zone (WEZ) method described in Bryan Litz’s book Accuracy and Precision for Long Range Shooting. This tool allows a shooter to see how his rifle can be expected to perform under a wide range of conditions, and how errors contribute in causing a bullet to miss its target.”

The WEZ tool appears to be doing what’s called a Monte Carlo simulation, which is a good way to model scenarios that have a certain level of uncertainty in the inputs. Monte Carlo simulations essentially play out hundreds or thousands of possible outcomes based on your inputs. The variables in each scenario are randomly populated within the ranges you set and according to a probability distribution. For example, if you gave some input that said your rifle was capable of holding a 0.5 MOA extreme spread, then it might play out one scenario where it drilled the exact point of aim, another where it hit 0.2 MOA high, another where it hit 0.25 MOA low, another that hit 0.12 MOA to the right, etc. Those shots would all still be within a 0.5 MOA group. It does that same thing for each of the variables in every scenario (muzzle velocity, wind call, range estimation, etc.), then it plays out each scenario, and plots where the shot would land. After it’s ran 1,000 different scenarios, it looks at the results of all of those and calculates your probability of hitting the target based on the variables you entered. Here is a screenshot of this part of the program, and I highlighted some of the key variables you can tweak.

Applied Ballistics WEZ Analysis Screenshot

I’ve played around with the WEZ tool a lot, and it was very enlightening! It challenged a lot of my long-held assumptions about how important different aspects were. As Bryan Litz said in his book, “Looking at each variable separately teaches us how to assess the uncertainties of any shot and determine how critical each variable is to hitting the target.”

The last post looked at what kind of impact group size had at long-range. In this post we’ll look at another element that we handloaders tend to fixate on:

How much does SD matter?

One aspect many of us handloaders chase after is really consistent muzzle velocities. That’s because if the muzzle velocity varies much, the faster shots will hit high and the slower shots will hit low. We often use standard deviation (SD) to describe how consistent our muzzle velocities are. I’ll try to not nerd out on you guys, but let me explain SD the quickest way I can. Standard deviation quantifies the variation in a set of data. Many shooters measure this by firing 10 shots over a chronograph, and then calculate the SD of that string of shots. A standard deviation closer to 0 indicates the muzzle velocities tend to be very close to the average, meaning they’re very consistent. A higher standard deviation indicates that the muzzle velocities are spread out over a wider range, meaning you can expect more shot-to-shot variation.

Okay, hang with me! Here is how SD applies to the real-world: You can see the common bell-curve below, which is known as a normal distribution. If you fire enough rounds, there is a very good chance your muzzle velocities will eventually form a normal distribution just like this. Since we know that’s what the distribution will eventually look like, we can use our 10 shot sample to estimate what the distribution would actually be if we fired 1,000 rounds. This is an approximation, but it’s a useful one. Each band in the diagram has a width of 1 standard deviation.

Muzzle Velocity Standard Deviation SD

If you had a standard deviation of 10 fps for your muzzle velocity, that means 68% of your bullets would exit the muzzle within 10 fps of the average velocity. That is + or – 10 fps, so if your average muzzle velocity was 3,000 fps, then you could expect 68% of your shots to be between 2990 and 3010 fps. Note that the extreme spread of those muzzle velocities would be 20 fps, not 10 fps … because it is always + or – the SD number. We also know 95% of your shots will be within 2 SD’s of your average. So 2 × 10 fps = 20 fps, and again it is + or – that amount. So with an SD of 10 fps and an average of 3,000 fps, you could expect 95% of your shots to have a muzzle velocity between 2980 and 3020 fps. That means you’d have an extreme spread of 40 fps for 95% of your shots. Remember, 5% of your shots would still fall outside of that range, meaning they’d be below 2980 fps or above 3020 fps.

Now you should have the basics of how standard deviation defines variation of your muzzle velocities with a single number. Let’s turn to Bryan Litz to tell us what we should expect in terms of SD for muzzle velocity:

“Regarding available ammunition types, a Standard Deviation (SD) of 20 fps is considered relatively poor consistency, and is generally representative of mass produced factory ammo. 15 fps is considered better than average for factory produced ammunition, but still substandard for those who handload their own ammunition. 10 fps or less SD is typically the goal of most handloaders, and very few commercially available ammo suppliers are capable of producing ammo with SD’s under 10 fps.”

It’s relatively easy for a reloader to produce ammo with an SD of 15 fps, but you have to be meticulous and use good equipment if you want to wrestle that down into single digits. I have a friend who has handloaded ammo for his 6.5×47 Lapua and 338 Lapua with an SD of 3 fps across 10 shot strings! I’ve witnessed it with my own eyes, and he’s done on multiple occasions. 3 fps is the lowest SD I’ve ever heard of, but it takes exponentially more effort to creep down into those lower numbers.

Now that we have context for what you can expect, or what is typically the goal … let’s look at what impact shrinking our SD has on the probability of getting hits at long range.

Effect of Muzzle Velocity SD on Hit Probability

Lowering your SD has a slightly bigger improvement on the further target, but we can still see the point of diminishing returns as the lines start to level off. In these scenarios, there is a big 5% difference from 20 fps to 15 fps, but only 2.9% improvement from 15 fps to 10 fps, and then just a 1% improvement in hit percentage going from an SD of 10 fps to 3 fps! This is primarily because, once again, most misses at long range are caused by wind and not vertical dispersion. Bryan Litz says “If you’re missing the target for reasons unrelated to vertical dispersion, then reducing vertical dispersion won’t improve hit percentage very much.” Well, it makes a lot sense when you say it that way! You can see what I’m referring to in the shot simulations below. We’re shrinking the vertical spread, but most of our misses are because of the horizontal spread … so we’re simply not addressing the primary cause of the misses.

How much does muzzle velocity standard deviation sd matter

One last point to keep in mind, is that all of this analysis assumes you have centered groups. That means they represent the best case scenario for hit percentage, since your odds only decrease if groups come off center. If you’re scope isn’t zeroed, or your rifle is canted slightly to one side, or your scope’s clicks aren’t calibrated correctly, or you pull the shot … then your hit probability can decrease dramatically. But these simulations assume we have all that stuff squared away.

Other Posts In This Series

This post was one of a series of posts that takes a data-driven look at what impact different elements have on getting hits at long-range. Here are some others posts in this series:
•How Much Does Group Size Matter?
•How Much Does SD Matter?
•How Much Does Cartridge Matter?
•How Much Does Muzzle Velocity Matter?
•How Much Does Accurate Ranging Matter?
•How Much Does Wind Reading Matter?
•Overall Summary

If you want to dig more into this subject or explore some of these elements for your specific rifle, ammo, and ballistics, I’d encourage you to buy the Applied Ballistics Analytics Package to run these kinds of analysis yourself. You could also pick up Bryan’s Accuracy and Precision for Long-Range Shooting book, which has a ton of great info on these topics and other aspects of shooting.

THANK YOU!! AIU.

I have the first three books, and placed an order for the other two volume set this afternoon.

Brian's sister Jennifer Fiorenzo is a real asset. I called at 4:29 and she made the effort to get my order label printed out, the two books packaged, and ran over to the PO to get them out today instead of Monday. Priority means I could have them Monday with a bit of luck. That is customer service.

Sounds like I am going to order the CD set next payday. There a lot of things many of us intuit, but never put into terms. WEZ is one of them I understand, but the importance of SD had escaped me until these posts today. I am grateful.

Another "Doh!" thing is Brian's book "Accuracy and Precision for Long Range Shooting". Think about the title and two very different components of winning matches or shooting Rockchucks.

Accuracy is centering your group in the center of the bullseye.

Precision, on the other hand, is the size of that group.

Simple, but I just assumed (yes, I know) the two were about the same thing. You develop an accurate load, then you just adjust the sights to center it at your desired range. Then, use the Litz ballistics charts, available free from Berger by going to their website and clicking on the Ballistics icon to show the projected drop/drift and remaining Velocity out to 2000yds.

Until a year or so ago, I had pretty much used either Jef Fowler's or the the JLK (Jimmy and Lois Knox) bench rest and varmint bullets. Twenty-plus years ago Jef worked with me and Bob Simonson (crafter of the most accurate bullet dies since/along side of Ferris Pindell; to design, and build the 110gr .257 ULD bullets. Today, I'm focused more on Berger, other than hunting bullets.

Thanks again,

Rich

Idaho;
Simply put, SD is the square root of the sum of the squares of each iterations difference from the average of the group.

How to find Standard Deviation

1.Calculate the Mean of your data set.
2.For each number: subtract the Mean and square the result.
3.Calculate the Mean of those squared differences. The result is called the Variance.
4.Calculate the square root of the Variance. The result is the Standard Deviation.
Important note- If the data set is only a sample of the whole population, change the formula to divide by one less when calculating the Variance. This is called Bessel's correction.

What does it really mean to a shooter?

Not much if you and your rig cannot shoot sub MOA.

Practically, one wants to achieve an ES and SD that ballistically equates to a vertical dispersion of the group at or less than half of the diameter of the target you intend to shoot at.

For example- in 223 heavy loads at 600 yds in High power- the X ring is 6 inch (~1 MOA) so your ammo need s to be able to result in less than ~.5 MOA dispersion vertically to assure that all of your shots, if you and your rifle can meet the challenge, will fall into the X ring. Thank fully the 10 ring is 2 MOA....

For this task, with an 80 grain 22 cal bullet, the SD and ES must be less than ~25 FPS and 10 or so fps SD.

Hope this helps....

PS- how you shoot over the chrono means a lot too- much of the variation of chronographing is the result of inconsistent firing for velocity readings. There is a book or essay on how to achieve as accurate and precise readings for shooting over a chrono too. I used to think my ammo was inconsistent until I began firing solely for velocity and not at a target while chronoing. Rigid rifle rest/brace, exactly repeating the firing procedure ( muzzle placement, angular alignment, lighting etc) All instruments have a capability limit- most inexpensive chronos are about +/- 3% , maybe more expensive ones are tighter....

As always, actual performance on target is the proof.

This is web site I use to calculate my SDs...

https://www.easycalculation.co...andard-deviation.php

Works great.

I was thinking about this topic later this morning- a few years back I was developing the best loads I could for high power use and my charts and numbers made me think that this 3 SD thing , as you indicate ISS, was in reality just a trip to making bad ammo. Not so in actual at-range testing though.

I saw my charts of 20 shots with SD lines built in showing that 18 or 19 rounds were actually at or less than the 1 SD line (+/-) and one or two out of a population would drop or rise into the 2nd or even 3rd SD lines. Well, 95% of my ammo over the test would certainly fall into the 2 or 3 SD ranges, but that simply was not good enough. I mean, I was getting ES of 16-28, SDs in 6-12 range ( once I cleaned up my chronoing technique). The same ammo would, from sling prone position at 300 yards, clean the target with high X counts, no unaccounted fliers and on the full course range at 600, I could score in the low 190s ( AR15 service rifle and aging eyes).

In short, my ammo, even the rounds that showed up as in the 3rd SD, would hit the 10 or X ring. (okay, in High power, the X ring is~1 MOA, the 10 Ring, ~2 MOA).

In short, carefully making ammo was providing rounds that would, every time, if I could, hit the desired target, even with 2 and 3 SD outliers. I quit all that data mining and barrel burning and focused on shooting 10s and Xs. My ammo-making technique was just fine.

quote:

Originally posted by Idaho Sharpshooter:
your comprehension level has slipped another notch. Add something that you have empirical data to support your statement. Otherwise you are just a jackass braying to hear himself.

SD assumes the more rounds you fire, the larger your groups will be. To back this theory up the theory also assumes the more rounds you fire, that your MV/SD will double, and then triple.

My contention is; if you have produced quality ammunition, the first and last targets you fire will vary less than 10% in group size. Groups do not go from 1 SD to 2 SD's to 3 SD's as the number of shots fired increases.

I am asking someone here with an IQ over 100, not someone in the low-80's like you to share knowledge.

I have Berger's Manual, and all of Brian's books. I have read them all, more than once. I spoke with one of Berger's Techs this morning about a simple working definition of SD. He tells me that SD is so complicated, that it takes a computer and pages of simulated and/or actual round count to figure it properly. In other words, it cannot easily be explained.

ES (extreme spread) is simple. The difference in fps between your slowest and highest MV.

AV (average velocity) is simple, it is the average MV of the number of shots fired.

So, based on your blathering, it does not appear that you have a clue as to what is either. The difference, is that I can admit it, and that you're incapable of explaining it or admitting your ignorance.

In plain english, it means you don't have a clue either.

To quote Brian Litz: SD is a better way to characterize variations in MV related group sizes (than ES or the actual sample group fired). He backs up this assumption as "One powerful way to use SD is through confidence intervals.

Who determines these "confidence intervals"?

SD can be used to make predictions about your data, and to assign a confidence to the prediction. Specifically, you can say that:"
68% of the shots should be within +/- 1SD of the average
95% of the shots should be within +/-2 SD's of the average
99.7% of the shots should be within +/-3 SD's of the average.

That means that 68% of your shots will be within +/- 1 SD, which, if you have an SD of 10fps grows your ES to 20fps.
That means that 95% of your shots will be within +/-2 SD's which, if you have an SD of 10fps grows your ES to 40fps.
That means that 99.7% of your shots will be within +/- 3 SD's, which means if you have an SD of 10fps your ES will grow to 80fps.

If that is valid, no wonder the group size gets larger, you are shooting crap ammunition or you are a really lousy shooter.

The closest he comes is in the glossary of Berger's book.

Standard Deviation: a statistical measure of variation within a group of data. Typically used to describe the variation in MV or the spread of shots in a group.

Drawings in the Berger Manual or all of Brian's books, tend to show computer generated plots of multiple groups (up 1000 simulated shots) to support the SD value.

In other words, the SD gives you a likelihood of how your data (velocity in this case) will be distributed around the average. He uses a bell curve to illustrate his theory.

Where I question this, is why the more shots you fire, SD says the larger your group sample size (cumulatively) will grow, and the higher your SD's will be.

I know somebody out there can explain this in real world terms.

Knowledge is what I seek, and enlightment...

Rich

Like I said, it is obvious in your post I quoted you have no idea what SD is; anyone who has ever studied statistics can tell that. SD is simple; you can calculate it with a piece of paper. Excel has several SD functions and so does SQL, R, and many other software applications.

I actually make my living (most of it) via a software company I founded that mines data for what are essentially flight recorders for factories. Our software is used to identify process issues and relies heavily on statistics such as SD (actually, COV normalized for a historical mean is a better calculation for lots of reasons). I have six patents on our statistical methods and a few others pending. So I guess if my IQ is in the low 80s I must be awfully lucky.

You are right: we have had issues - maybe it was the time you claimed to have shot 30 (?) 350 point elk but left the antlers because you only hunt for meat. Or maybe it was all the PMs you sent to folks threatening to squash them like a bug. I could go on and on. You have had issues with lots of folks on AR, not just me.

I get a lot from guys like HPMaster and Instructor; not so much from you. I am sure you feel likewise, but life goes on.

By the way, had a fabulous time in Mexico fishing and scuba diving. Nice to know a guy with an IQ in the low 80s can be lucky enough to hire smart people to run his businesses so he can go out and play. Only in America.

good to hear. I figured you went to Mexico for the peach pit treatment...

quote:

Originally posted by Ackley Improved User:
What are the SDs of the velocity spreads for your long range ammo reloads?

My LR rifle does double duty for hunting and targets. For the last 10 years I've been using the same reload for both. Averaging the SD from chrony results over these years I get 11.8 and a CV average of 0.40%. Yet can still detect the on set of some vertical stringing in my groups beginning at 400 yds.

All I ask here is for any response to be accurate, and add to the knowledge base.
A-N-Y statement you have read by me is easily backed up with references and good data.


montea6b,

My primary chrono is an Oehler 35P. Know what "P" stands for? I also own a M43. Know what that is used for?

Secondly, I have always had a low tolerance for stupid...

Not trying to get off the subject however, I found an article by the US Shooting Team that may be relevant. I can't find it any longer so you'll have to be stuck with my copy.

Sorting Match-Grade Bullets for Long-Range Accuracy, Where to Begin?
WARNING: All technical data in this publication, especially for handloading, reflect the limited experience of individuals using specific tools, products, equipment and components under specific conditions and circumstances not necessarily reported in the article and over which the National Rifle Association (NRA) has no control. The data has not otherwise been tested or verified by the NRA. The NRA, its agents, officers and employees accept no responsibility for the results obtained by persons using such data and disclaim all liability for any consequential injuries or damages.

Sorting of bullets for extreme long-range accuracy is not difficult to do, but some background in theory is needed. In this article, we will begin with the basics and end with “extreme bullet sorting,” which we've long found beneficial to our long-range rifle accuracy. Using this technique, a capable competitor can shoot a 1.319 inch five-shot group at 1000 yards.

First, the vast majority of the centerfire rifle ammo our teams use does NOT employ sorted bullets. We do test samples of each new bullet lot at full distance before it is fielded to the teams, to ensure a high level of accuracy. Excellent rifle accuracy can easily be obtained using standard, high-quality match bullets without sorting. So, unless you have a specific NEED to sort bullets, feel free to add points to your score through practice, rather than obsessively fretting about your bullets!

Here at the U.S. Army Marksmanship Unit’s (AMU) handloading shop, we only sort individual bullets for the most demanding long-range applications and competitions. Only the most accurate rifles and shooters can fully exploit the benefits of this technique. The basic sorting process involves measuring the Overall Length (OAL) of the bullets, and grouping them in 0.001 inch increments. It's not unusual to find lots of match bullets that vary as much as 0.015-0.020 inch length throughout the lot, although lots with much less variation are seen as well. Even in bullet lots with 0.015 inch OAL variation, the bullet base-to-ogive length will show much less variation. Hence, our basic sort is by bullet OAL. One obvious benefit of sorting is easily seen in the below photo. The few bullets that are VERY different from the average are culled out, reducing probable fliers.



Bullet-sorting “histogram” shows the typical bell-shaped distribution curve.
So, where to begin? How does one know what OAL increments to use when sorting? The answer is simple. As each lot of bullets is unique in its' OAL distribution, it's best to sample your bullet lot and see how they are distributed. In the above photo, you will see a set of loading trays with a strip of masking tape running along the bottom. Each vertical row of holes is numbered in 0.001 inch increments corresponding to the bullets' OAL. A digital caliper makes this task much easier. As each bullet is measured, it is placed in the line of holes for its’ OAL, and gradually, a roughly bell-shaped curve begins to form. The photo posted here is of a bullet sample set (“histogram”) in the early stages.

Note that near the center, bullets are much more plentiful than near the edges. At the extreme edges, there are a few that differ markedly from the average, and these make great chronograph or sighting-in fodder. We recommend using a sample of 200 bullets from your lot, and 300 is even better. Some bullet lots are very consistent, with a tall, narrow band of highly-uniform bullets clustered together over just a few thousandths spread. Other lots will show a long, relatively flat curve (less uniform), and you may also see curves with 2 or more “spikes” separated by several 0.001 inch OAL increments.

Now we can see what percentages of bullets will fall into very uniform groups. How do we know what size OAL groups for sorting? The answer is, it depends on your application.

When setting up your bullet sorting operation, your method will be determined in large part by the purpose for which you intend to use the bullets. For example, if you are preparing for an extremely important long-range match, you may choose to do a double-sort (first by OAL, and then by base to ogive, using a bullet comparator. This will be covered in detail in Part 3.) However, this is very time-intensive and requires a relatively large basic lot to winnow down to a usable quantity of super-sorted bullets.

For most important long-range (LR) uses, a single sort of good match bullets by OAL is likely to be sufficient. Using the sample/histogram as shown in our previous article, you will see that based on your particular lot of bullets, they will fall into certain groups by 0.001" increments. Here at the AMU, on the rare occasions that we sort bullets, we are fielding ammunition for a number of shooters in any given event; thus, our need for sorted bullets is for relatively large groups.

Therefore, we may often combine groups of 0.001" into lots of 0.003" variation. Thus, say, .005", 0.006" and 0.007" sorts will be combined into 1 lot. Then, the next bullet lot might be sorts 0.002", 0.003" and .004". The histogram will tell you the most plentiful increments to expect when sorting, and what your logical combinations will be to get the largest 0.003" ranges of bullet OAL's.

However, for individuals, loading for a single rifle, the sorts can be much tighter. Depending on the size of the initial bullet lot, you may have many batches of bullets, all grouped into 0.001" increments, that you can use to load individual ammo lots with. Keeping track of the original sort length (say, 0.005") used in the match ammo lots allows using ammo lots with adjacent 0.001" sorts for ultimate consistency. I.E., after you shoot up the lot with all 0.004"-length bullets, the next logical lot to use would be either 0.005"-length bullets or 0.003"-length bullets, for minimum variation between lots.


Another, less time-intensive approach is to look at your histogram and evaluate the "peak" and adjacent 0.001" sorts. See how many naturally fall into a 0.003", 004", or even 0.005" spread of adjacent 0.001" increments. If you find that, say, 60 percent of your bullets fall into the desired range of OAL's, you might decide to just use that center 60 percent for important matches.

The remaining bullets—the left and right "tails" of the bell curve—are fine for practice and other less-important uses. Keeping all the "left tail" bullets together as a batch, and "right tail" bullets together as another batch will reduce inconsistency vs. combining them all together. Naturally, that would result in a wide spread of OAL's with a gap in the middle where your match bullets were removed.

Tip: This is a small, common-sense tip learned the hard way by this writer many years ago that might save you some trouble someday. While driving to a rural range about an hour from his house to test assorted long-range recipes for accuracy, he had his test ammo meticulously arranged by type in loading blocks (not sealed ammo boxes, hint hint), sitting neatly arranged on the passenger seat of his car.

Making good time on a rural road near the range, he rounded a curve and noticed a mobile home on the right, with a cat sitting by the side of the road. He continued on, as the cat showed no intention of wanting to cross the road. At the last second, the cat dashed into the road, and our hero slammed on the brakes, narrowly missing the feline dare-devil. However, all his meticulously prepared test ammo slid off the seat and onto the floor, where they were all jumbled together out of order.

A lot of bench-work was wasted that day, and ever since, this writer has marked his test-recipe ammo with a Sharpie marker in case of another such "cat-astrophe". (Sorry... just couldn't resist!) After policing up the remains of a lot of meticulous work, the writer Almost wished he'd just hit the accelerator instead of the brake ... almost!

Over the years, the system has evolved to using one, two or three stripes on the sides of the projectiles to denote particular powder charges or OAL increments. By marking the projectiles rather than the cases, when the rounds are fired, the ink is gone, and cleaning cases by tumbling is significantly easier than it would be if there were ink remaining on the cases. If there are several test batches, different colors of ink are used as needed. It doesn't take long to run the marker along a row of bullets in a loading tray to make a small stripe on each, and the peace of mind is reassuring.


Hope it adds to the conversation.