Category Archives: Reloading Corner

RELOADERS CORNER: What I do…

Facebooktwittergoogle_pluspinterestyoutube

There are a lot of ideas and options when it comes to loading the “most important” ammo. Here’s the 5-step process I ended up with… READ MORE

dial indicator

Glen Zediker

I spend a lot of time telling everyone else what they should do, and probably more time telling them what not to do, or what they could do… I thought it might be best to tell you all exactly what it is that I do to prepare a batch of ammo for a tournament.

That’s a quick way to show you what, clearly and obviously, matters to me. I admit: I don’t always do all the things that I talk about. A big part of my role here is to pass along information, answer questions before they’re asked, in a way of looking at it. There’s information, and then there’s action, and that’s not a contradiction, to me. For instance, I can tell you all about case neck turning, and metplat uniforming, and many other preparation steps. I have done them all, sometimes do them, but dang sho not always.

Believe me: I have tried everything and much, much more than I’ve ever talked about in these paragraphs.

Following is what I have found works to my satisfaction. Since I’m dealing with a fair amount of cartridges at any one time, there is, no doubt, a time and effort element that’s important to me. In other words, what’s coming next are the things I really think I must do to give my score the best boost I can reasonably give it.

Step One: Get my cases together and size them. I load in 100-round batches, so I start with five boxes, or whatever corresponds to 100 rounds. Without so much as a second glance, I run them all through my full-length sizing die: lube each and cycle it through. If nothing else, most new cases are not nearly ready to load. The case necks are usually banged up, not round, so at the least I’d need to size the inside and outside of the case neck, and I’ve found that, while other appliances will suffice for that, it’s just easiest to use my sizing die.

Step Two: I trim them all. This isn’t done as any matter of safety, just consistency. I set my trimmer to at the least touch each case mouth. This is very important! The next prep steps rely on having cases that are all the same length.

case trimming

Step Three: After chamfering inside and outside (I use a 17-degree on the inside and a standard tool for the outside) I run a flash hole uniformer through each. This is why it’s important to have them all the same height. That way the uniforming tool cuts to a consistent depth.

inside uniformer
After full-length sizing all my new cases (to mostly get the necks shaped up), I trim all the cases to ensure length consistency to start, because the next procedure, inside flash hole deburring, demands it. Shown is from Hornady. CHECK IT OUT HERE

Step Four: Primer pocket uniforming. I run each through this process. Now, I have had some lots of brass that make this normally simple process a chore, and that’s because the reamer is too snug a fit to the pocket. We all know that primer pockets are at their smallest on new cases. That is, by the way, one reason I’ve mentioned that the primer pocket “feel” is a leading indicator after the first firing as to the pressure level of the load. In keeping, there are times when I wait until recycling the first-fired cases before running the uniformer. It depends on how readily the cases will accept the reamer.

primer pocket reamer
Primer pocket uniforming is an important step in my own process, but sometimes I wait until the first-firing. Depending on the tool used, and how much power can be applied to assist, this job can be a chore on a tight pocket. Shown is a Lyman tool. CHECK OUT TOOLS HERE

Note: I consider my “best” ammunition to be that which I load on my once-fired cases. At the same time, I won’t hesitate to use new cases for a tournament (but not for a Regional or bigger event). Over a whopping lot of time keeping notes, my “second-firing” rounds tend to shoot a tad better, but it’s a miniscule amount. That’s why I don’t really sweat over the primer pockets on the first go-around.

Step Five: Roll them all! I run all the cases through a concentricity fixture, aka: spinner, to check runout. I segregate on the following criteria: “flatliners” no visible runout, less than 0.001, 0.001, up to 0.0015, more than that… Five piles. One reason I do 100-round batches is because I need, technically, 88 rounds for a tournament. Since I am using “name-brand” brass, I easily find my 44 prone-event cases that are going to be no more than 0.001 out of round. The remainder are proportioned better to worse for the 200 yard events. It’s not that I don’t think each round matters, because it does, and, honestly, the 200-yard Standing event is what wins a tournament, but that’s way on more on me than the ammo. A case with 0.015 runout is not going to cause a “9.” That case will produce groups way inside the X-ring.

Co-Ax Case and Cartridge Inspector
I segregate using a runout indicator, a tool shown before in these pages. Some argue, logically, that the best way to find cases with the most consistent wall thicknesses is to measure wall thickness, but, my experience has shown that, ultimately, concentricity is the result of wall thickness consistency. Sho is faster. Shown is a Forster Co-Ax Case & Cartridge Inspector

Now. I fully realize that segregating by runout, concentricity (“centeredness”), is not the same as actually measuring case neck wall thicknesses. However! “Flat-liners” are what ultimately result from consistent case neck walls. Since I have also sized the inside of the case neck, not just the outside, the spinner does give an accurate indication of case neck wall consistency.

case segregation
After sorting by runout, here’s what I get, or what I got once… These were graded (left to right) 0.0000 (no perceptible runout), up to 0.0010, 0.0010, 0.0015, and more than that. So, here, there were 37 cases that were at or near the level of neck-turned cases, and another 37 showing only 0.001, but way on easier.

Since it’s often the night before that I’m doing this, spinning is way on faster than measuring…

Then I prime, fill, seat. Get some sleep.

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: Meter Use Tips

Facebooktwittergoogle_pluspinterestyoutube

How well you set up and operate a powder meter has a lot to do with ammo consistency. Here are a few tips on getting the most from this tool. READ MORE

Glen Zediker

Going back to our last conversation, the topic was dispensing propellant charges, and whether to weigh each charge or dispense each charge using a powder meter. Generally, most seem to agree that weighing each is the sure way to better consistency. I don’t always agree with that, and I say that mostly because my chronograph and group size numbers don’t support superiority of either approach. However! I sure do know that metering charges is way on faster and easier than weighing them all out!

Once again: the only answer that works is to experiment for yourself and settle the question based on empirical evidence. Right: shoot it and see!

This next offers a few tips I’ve had good success with over the years. I can tell you that, without any doubt, learning how to set up and operate a meter has a decided influence on those chronograph and group size measurements.

scale weight
I am adamant about following this process to set a meter: Don’t throw and weigh single charges to adjust the meter. Throw and weigh 10-charge portions, with the scale set, of course, to 10-times the desired single-charge weight. I do not recollect one time when my meter adjustment did not change following this process from what I first arrived at weighing single throws. Here’s how I set it to adjust for a 24.0 grain throw.

First: I very strongly recommend setting the meter throw based not on one single charge, but on multiple charges. Here’s my method: After running a few single throws to get it close, I set my scale to 10 times the desired single-throw propellant charge weight, then throw 10 charges into the scale pan. I have done this (so) many times over (so) many years that I can tell you that I have no memory or record of this tactic not influencing the final setting I have dialed in. Do this 3-4 times and see what you see. There’s a huge likelihood there will be an adjustment needed. And for some reason, supported by my notes at least, the final setting is usually a tick lower than I gauge for one-throw-at-a-time weight checks.

Now, I know that if the meter is accurate then each single charge will weigh what it should, but maybe the difference that makes this method work best is that scales aren’t perfectly accurate. Maybe it’s the damping system, or continual issues with calibrations, but a 10-throw lot ultimately results in a more precise setting. I’ve proven that too many times to myself to qualify it with a “may.” No, it does.

As mentioned in a past article, the smaller the propellant granules the more precise each fill can be. Longer-grained kernels provide more air space and “stack” more than smaller-grained kernels. It’s also clear that the higher degree of precision on the meter internal sliding surfaces, the more “clean” the strike-off will be.

And, meter operation has a whopping lot to do with the consistency of filling the meter drum. Just like tapping a case bottom settles the propellant to a lower fill volume, same thing happens filling the drum in a meter.

powde meter operation
Not too heavy, not too light. Work the handle the same each time, and have it come to a positive stop. “Thunk. Thunk.” Focus on a consistent speed. This has a huge effect on how consistent the throws will be.

The trick to good throws is working the meter handle consistently, and also settling on a contact force when the meter handle comes to a stop in the “fill” direction: It should bump but not bang… I wish I could be more clear on that, but it’s a feel. Don’t go too slowly, gingerly taking the handle to its stop, and don’t slam it there either. You want a positive, audible “thunk” when the handle stops. If it’s the same each time, fill consistency will, not can, improve. Focusing on operating the handle at a constant rate of speed teaches this in short order. It’s a positive movement that, for me, takes about one second to lift the handle.

harrells meter
I recommend longer drop tubes (meter or funnel). The longer tube has the same effect as tapping the case to settle the propellant. This helps in loading stick propellant into small-capacity cases. Rubber-band a dryer sheet around the propellant container to static influence, which can be an influence, especially in the Western regions.

There’s a few more tips in the photo captions, and here’s another: Do not leave propellant in a meter! Return it to a sealed container when you’re done for the day.

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: SD Pt. 2

Facebooktwittergoogle_pluspinterestyoutube

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

Facebooktwittergoogle_pluspinterestyoutube

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.

RELOADERS CORNER: Bullet Ballistic Coefficient

Facebooktwittergoogle_pluspinterestyoutube

Ballistic coefficient is a term that’s often used but sometimes not fully understood. Keep reading to find out exactly what it is, and what it isn’t…. HERE

nosler rdf
BC is essentially a race between a real bullet and a mathematical bullet. Real bullet never wins… The closer the real bullet gets to the “standard” bullet, though, the higher its BC and the better it’s going to fly. I’d love to get a Kroger-sack full of G1s… Until then, one of these Nosler RDFs will do nicely.

Glen Zediker

A “ballistic coefficient,” or “BC,” is a number that suggests a bullet’s aerodynamic performance.

BC is a component in bullet design that matters much, and it matters more the farther it travels. Bullets that flat out fly, fly flat far out, are of great interest to any longer-range shooter. A bullet with a high(er)-BC is also an advantage at shorter distances, especially when there are variations in the shooting distance. A flatter-shooting (one of the traits supported by a higher BC) bullet means a more flexible zero, a smaller difference in the elevation hold from, say, 100 to 300 yards. BC is influenced by sectional density, bullet weight, and, mostly, its shape or profile.

BCs are derived by comparison. Here’s how that works: There are “standard” bullets that are mathematical models. Bullet designers and ballisticians know which model to apply to different bullet styles. Pistol bullets, for instance, are calculated from (compared to) different models. For the majority of rifle bullets we’ll encounter, one common model is a “G1” (there are others, like G7, which is becoming the popular standard for boat-tail bullets; G1 is based on a flat-base). The flight of this G1 bullet has been calculated at varying velocities and distances. It’s “all math” because a G1 doesn’t exist in a tangible sense.

vld blueprint
Here’s a bullet blueprint. It’s the Bill Davis original 105gr 6mm “VLD” (very low drag). Design factors that influence BC are pretty much every design factor: length, ogive, boat-tail, meplat, weight. All these factors, in this instance, calculate a BC of 0.560. By the way, there’s about a 5 point BC increase for each added 1 grain of bullet weight.

The standard bullet has a BC of 1.000. An actual bullet that’s compared to, for example, the G1 at points, distances downrange, will either be flying faster or slower than the G1 model. If it’s faster, its BC will be greater than 1.000; if it’s slower, it will be less than 1.000. So it’s a percentage of the standard or model bullet’s performance.

Comparing bullets with different BCs, the one with the higher number loses less speed over distance. Losing less speed means its flight time will be shorter and it won’t drift and drop as much as will a bullet with a lower BC. So, a 0.600 flies better than a 0.550.

Depending on the bullet-maker, assigned or published BCs are either calculated or measured. More mathematics than I can wrap my mind around can get these calculations done based on a blueprint. Measured BCs involve chronographing at the muzzle and then at other points on downrange, same bullet, same flight.

Which method — math or measure — provides the best information? Some, and this only “makes sense,” believe that a measured, tested BC is more realistic and, therefore, more valuable. But, if the point is to compare bullets, calculated BCs might be more reliably accurate. I know a number of very serious NRA High Power shooters who have gone to great lengths to “field test” different bullets. It’s not easy to chronograph at long range. Given that information, measured BCs are quite often lower, but not nearly always. Reasons follow.

All the drift and drop tables (whether printed or digital) you’ll see are based on a bullet’s assigned BC. The accuracy of those tables clearly revolves around what the actual, at that moment, BC performance is from the bullet you’re shooting. Also, some bullets have a different stated BC based on muzzle velocity to start.

A whopping lot of things affect the actual, demonstrated BC: anything that can influence bullet flight influences the actual BC performance.

Bullet stability is a factor. For a stated BC to be shown on a shot, the bullet has to be “asleep.” If it’s not stable, it’s encountering disruptions that will slow it down. The rotational speed of a bullet in a test can influence BC. We’ve seen differences comparing different twist-rate barrels, and the faster twists often show a little lower BC outcome.

Atmospherics, which add up as a list of factors, influence BC mightily. Air density is probably the most powerful influence. Any conditions that allow for easier passage of a bullet through the air don’t detract as much from its BC as do any conditions that serve to hinder its flight. BCs are based on sea-level so can easily show as a higher number at a higher elevation.

uniformed meplat
BC uniformity is important to a long-range shooter’s score (less elevation dispersion results). There will be variations in any box of hollowpoint match-style bullets, and a source for variation is the meplat (tip). These variations are the result of the pointing-up process in manufacture. I’ve measured as much as 0.020 inches sorting through a box of 100. A “meplat uniformer” tool eliminates this variance. Uniforming reduces BC 3-4 points, but it’s a trade many serious long-range shooters say is worth the effort. Uniformed on right.

meplat uniformer

Range-realized reality is that the demonstrated BC changes from morning to afternoon and day to day and place to place. The calculated BC is not changing, of course, but the mistake is assuming that a BC is a finite measure of bullet performance. If you’re interested, there’s some valuable information from David Tubb (visit DavidTubb.com). He’s done a volume of work on calculating influences from atmospherics as it applies to his DTR project, which, in one way of seeing it, gets down to understanding why it’s really rare to dial in what a ballistics table says for a particular bullet and speed and distance, and hit the target.

One last (for now) bit of information I’ve always found valuable: a BC is a finite thing in one regard, and that is that any BC derived from a G1 model, for instance, fits all bullets with that same BC. This was helpful before ballistics apps were as common and easy as they are now. For instance, if there was a new .224-caliber bullet with an advertised BC, but no tables, just find another bullet, of any caliber, with that same BC, plug in the velocity, and the drift and drop figures will be accurate.

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: Bullets 101

Facebooktwittergoogle_pluspinterestyoutube

Bullet structure should play an important part in your selections. Here’s a short course in bullet architecture, and why it matters!

224 bullet comparison
There’s probably a wider variety of .224 caliber bullets than any other diameter, and there are whopping differences available! Left is a Hornady 35 V-Max, right is a JLK 90gr VLD. That’s the longest .224 I’ve had to work with.

Glen Zediker

These days we don’t have to settle for much of anything. Pretty much whatever it is, there are options. That’s a good thing, as long as we figure out how to sort through all the options. I didn’t count them all, but there are way on more bullets available now than ever. This article sets out to help you all understand the essential engineering of this all-important ammo component.

The reason there are so many bullets is because there are so many different ultimate uses we put them to.

All bullets are designed or intended to do something, and, clearly, the first idea is to hit a target.

There are bullets engineered to perform variously on target, including the proximity of impacts on target. I say it that way because a “match” bullet’s job is to perforate a piece of paper. A bullet designed for varmint hunting, on the other hand, is designed to produce explosive impact, and one for larger game hunting strives to strike a balance between expansion and penetration. All bullets have to meet their target to be effective, and different premiums often also result in a few trades. Specialty hunting projectiles, for instance, don’t usually out and out group as well as those engineered for target shooting.

However! No matter how it’s built inside, there are universal elements of any bullet design, and those are found on the outside.

bullet parts
Here are the pieces-parts of a bullet. Each element is influential not only in downrange performance, but also in how tolerant or flexible the bullet will be in different rifle chamber and cartridge structures.

Bullet parts: base, that’s the bottom; boat-tail, or not (flat-base); shank, portion of full-caliber diameter; ogive, the sloping “nosecone,”; tip, either open or closed (open it’s called the “meplat”). The shape of the ogive and the first point of “major diameter” are extremely influential elements. The first point of major diameter can vary from barrel brand to barrel brand because it’s the point on the bullet that coincides with land diameter in the barrel — the first point that will actually contact the barrel as the bullet moves forward. When there’s a cartridge sitting in the rifle chamber, the distance or gap between the first point of major diameter and the lands is called “jump,” and, usually, the less there is the better. More in another article.

bullet bearing area
This gives an idea of bearing area. The point that contacts the lands is the first point of “major diameter,” and from there back down the body is what will be in contact with the barrel. Longer area means more tolerant behavior, but lower potential velocity.

The first point of major diameter and the shank combine to determine the bullet “bearing area.” This is how much of the bullet is riding the barrel surfaces. Usually, bullets with greater bearing areas tend to shoot accurately, but, might not get to velocities as high as one with a shorter bearing area. Longer bearing area creates more drag in the bore. Longer bearing area bullets also tend to be more tolerant of jump.

magazine box rounds
This is the round architecture that matters the most to the most of us. We need good on-target performance from cartridges with bullets seated to feed from a box magazine. Choose a tangent profile that’s no more than 8-caliber ogive.

The two essential profiles a bullet can take are “secant” and “tangent.” This refers to the shape of the ogive. A tangent is a more rounded, gradual flow toward the tip, while a secant is a more radical step-in, more like a spike. Secants fly with less resistance, but tangents are more tolerant of jump.

tangert and secant
Tangent, left; secant, right. Tangent ogives are more tolerant of jump, but not quite as aerodynamic at extended distance.

Ogives are measured in “calibers.” That’s pretty simple: an 8-caliber ogive describes an arc that’s 8 times caliber diameter; a 12-caliber is based on a circle that’s 12 times the caliber. The 8 will be a smaller circle than the 12, so, an 8-caliber ogive is more “blunt” or rounded. (So I don’t get comments from engineers, there’s more to it than this, as it applies on blueprints to different profiles; it’s the ratio of its radius to the diameter of the cylinder. But my description is accurate as an overview.)

Bullets with lower-caliber ogives are more tolerant of jump and (usually) shoot better, easier. Higher-caliber ogives fly better, farther. This is an important component in the “high-BC” designs. Same thing comparing tangent and secant: the first is easier, the second beats the air better.

bullets compared
Here’s a good example of the differences in bullets. These are both 75 grains. The one on the left is engineered to be fired from a magazine-length round; the other is engineered to provide better performance over more distance, and it should not be fired at magazine-length. Look at the ogives closely and see the curve difference.

When you see terms like “magazine bullet” or “length-tolerant bullet” that is referring to those with tangent profiles and lower-caliber ogives. (“Length-tolerant” means that it’s not sensitive to seating depth.) If you want to experiment with the longer “high-BC” style bullets, you might find they don’t group well until they get close to or right on the lands when the round is chambered.

More soon…

Check Midsouth for a massive selection of bullets of all calibers HERE

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: Pressure Signs

Facebooktwittergoogle_pluspinterestyoutube

We usually want the most velocity we can SAFELY get, and here’s all about how to stay safe. Keep reading!

Glen Zediker

I’ve been on the topic of load development — “working up” a load — for the past couple of editions, and, based on the excellent feedback from you all, here’s more. As always, there’s only so much I can write before I have to cut myself off.

I’ve said that velocity is the initial leading indicator of pressure. Velocity, in itself, however, is not a definitive indicator of pressure. I’d like to clarify… The first point is that I am a big believer in establishing a goal for load development, and, for me (and likely most others) that is a velocity. Accuracy is a given! I will never consider a combination that’s not shooting little knots downrange, but accuracy and velocity are not mutually exclusive. I also would never consider a combination that produced very small groups at an unacceptably low velocity, and that’s because I’m shooting (always) beyond 200 yards. The super-accurate low-velocity load gets its bullet shifted that much more in a variable wind, so it’s way on less likely to maintain those small groups.

I want to hit the velocity ballpark I have in mind and that’s why chronograph readings as I’m incrementally increasing the propellant charge are my leading indicator to how close I’m getting. I am also, always, looking for pressure signs on the spent cases — each and every one ejected.

So about those pressure signs…

Primer condition gets first attention.

primer pressure signs
Middle is what I want to see: pretty much a new primer with a nice round dimple in the center. Right, well. Massive pressure! But notice that the primer still shows a radius on the edges and is only a little rougher in appearance, well, aside from the crack…

A primer should have a smoothly dimpled firing pin indention, a shiny appearance, and a visible radius on its edge. If any of those are missing or compromised to varying degrees, there’s your sign… A dull and flattened primer has been abused, as well as one with a pitted or cratered appearance. Clearly, a crack or leak (indicated by black fouling) is way over the limit. After experience, backed up by gauged measurements, you’re liable to find that judging what’s “normal” and “safe” from one rifle can be different from another. I have had individual guns that flattened primers at any point near a safe-maximum charge. And, I’ve had them that just lied. Unfortunately, small-rifle primers don’t show always show pressure signs as reliably as large-rifle primers (structural differences). I’ve had experiences where the primers are all nice and shiny like and then blow out with the next increment. Shame on me for taking it there, and, speaking of: don’t get greedy! That’s one reason a velocity goal is important. Despite what your kindergarten teacher told you, you’re not that special… If you’re reading another 50+ feet per second more than what consensus says you should, better bet you’re over-pressure. “We” went through a lot of that when coated bullets got popular: those changed all the rules for “maximums.”

flattened primer
Here’s flat. My experience has been that large-rifle primers tend to display this indication more so than small. What’s happened is that the primer has flowed quite forcibly to fit the confines of its pocket and the bolt face. It’s also normal for some rifles, but that just means you have to know: pay attention and back off if you see a flattened primer.

The best pressure indicators show at the loading bench.

primer seating
My best “gage” for pressure is seating a primer in a fired and resized case. It’s a feel, gained through comparative experience, but too easy means there was too much pressure.

The reason I suggest (strongly) doing load work-up with new cases is because you then have a baseline. Measure the case head diameter (on the case, not the rim or groove) on the new case and compare it to the fired case. Up to 0.0005 (that’s ten-thousandths) is really high but some say acceptable (not me), and 0.0002-0.0003 is what I’d prefer. Plus, since a new case is at its smallest, meaning it will have a little less capacity than a fired case, you’re getting some assurance that the pressure will likely be a little lower from the same load in subsequent reuses of that case.

All dimensions are at their minimum in a new case. Primer pocket expansion is related to case head expansion. I get (what’s proven to be) a very accurate indication of pressure based on the resistance to seating a primer in that resized case. You have to use a priming tool that gives adequate feedback (meaning low leverage) but if the primer just slips right back in, that load was over-pressure. In a more extreme circumstance, the primer won’t stay seated. Yes. I have seen that. Shame on me, again.

Finally, a new case easily points out the difference between a “pressure ring” and a “sizing line” that can show just above the case head along the case body. A bright ring there indicates excessive stretching (a sizing line comes from the die reducing that area, and is perfectly normal). That “pressure ring” sign is also likely an “improper headspace” sign, but that’s another article.

pressure ring
Here’s a “pressure ring.” This poor old fellah used to be a brand-new Lake City Match case. I suspect there was some issue with this rifle’s headspace, but if you see this bright stretch mark, red flag it! It means the case is going to crack right there next use (called an “insipient head separation”).

Pierced Primers
This is a common malady on AR-platform guns, and especially on the big-chassis versions (SR-25, AR-10, and similar). Pressure both isn’t and is the culprit and the solution. Lemmeesplain: What causes the pierce is a firing pin hole that is too large. It is not the fit of the firing pin tip to the hole! An engineer can explain it, but it has to do with surface area covered by the firing pin hole, and then along with it the surface area of the primer. Simply: the firing pin hole turns into a cookie cutter. A primer pierce creates all manner of ills, including wrecked firing pins, gas flow through the charging handle area (where your face is), and abrasive debris scattered throughout the lower interior, including the trigger parts.

firing pin hole size
Blueprints call for a 0.058-inch diameter firing pin hole on an AR15 bolt. If the hole is too large then primer structural failures (pierces) will, not can, rear up. Too big is anything more than 0.062 inches, and I’ve seen plenty bigger than that. I use machinist’s drill bits to quick-check bolts: 1/16 (0.0625) and #53 (0.0595). If the first fits the hole, find another bolt. If the #53 won’t go, use that bolt with confidence.
pierced primer
Notice that this primer doesn’t really show excessive pressure signs. Just has a hole in it…

Excessive pressure gets blamed for a pierce but what’s really going on there is that it’s not certain that amount of pressure would be judged as “excessive.” It’s just gotten high enough to bring on this result. So, yes, lightening the load will stop the piercing, but, in my experience and that of many others, the pierces can start happening before reaching what most might agree on is a max load. I say that because “we” are all shooting about the same bullet/primer/case/propellant combinations in NRA High Power Rifle (with respect to Service Rifle division AR15s, for instance). Seeing pierced primers before hitting the proximity of competitive velocities points to “something else,” and that is the firing pin hole.

In a truly over-pressure load, the primer can crack or blow slap out, but it won’t pierce.

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: Incremental Load Work-Up

Facebooktwittergoogle_pluspinterestyoutube

To get the most from your load testing, in the shortest time possible, learn the “Audette Method,” and put it work for you. Here’s how!

sight in target
Use a target that’s, one, easy to line up on, and, two, lets you make notes on the target itself. I usually circle and note the 3-shot increments, or you can add a number by each shot hole to indicate which try they belong to. Midsouth has some HERE

Glen Zediker

Last edition I suggested taking the step toward putting together a “portable” loading setup to allow for load development right at the range. This time I’ll talk about an idea on getting the most out of a test session in the quickest and surest way.

I have followed an “incremental” load work-up method for many years, and it’s served me well. Some call it the “Audette Method” named for the late and great Creighton Audette, long-time long-range and Benchrest experimenter.

Backing up a bit: Being able to employ this method efficiently requires having spent the preparation time, doing your homework, to know exactly how much “one click” is worth on your meter. Whether the meter clicks or not, it’s the value of one incremental mark on the metering arm. The value of that click or mark varies with the propellant, but by weighing several examples of each one-stop variation (done over at least a half-dozen stops) you’ll be able to accurately increase the charge for each test a known amount.

harrell's meter mounted
I count on a Harrell’s Precision meter. Its Culver mechanism allows for easy and accurate incremental adjustments in working up a load. The dryer sheet eliminates static electricity.

I usually test at 300 yards. That distance is adequate to give a good evaluation of accuracy and, for the purposes of this test, is also “far enough” that vertical spreads are more pronounced. Testing at 100 yards, sometimes they all look like good groups… So it’s at about 300 yards where we’ll start to see more difference in good and bad.

Get to the range and get set up, chronograph in place. Put up a target. Use whatever gives you a clear aiming point, but it’s helpful to have a light background not only to see the holes easier using a scope, but also to make notes on. More about that in a minute.

Use the same target for the entire session. (Put pasters over the previous holes if you want, but don’t change paper.) The reason for using the same target for the whole session is that helps determine vertical consistency as you work up through successively stouter propellant charges.

I fire 3 rounds per increment. As it gets closer to “done,” I increase it to 5 or 6. At that point I’ve hit a couple of speed points, two or three increments that represent a performance level I can live with (one is on the “iffy” end of the pressure, and I rarely choose that one) and am focusing more closely on group size. Final confirmation comes with one 20-round group. For what it’s worth, I usually pick the one in the middle.

A 3-round volley might seem inadequate, but it’s not if there’s confidence that the rounds are being well-directed and speed is being monitored. If I’m seeing more than 12-15 fps velocity spreads over 3 rounds, I’m not going to continue with that propellant. Same with group size: if it’s a big group over 3 rounds, it’s going to be a bigger group later on.

I’m sho no mathematician-statistician, but from experience I’ve found that, while certainly there’s some probability that the first 3 rounds fired might represent the extreme edges of the load’s group potential, and that all the others are going to land inside them, uhh, that’s not even a little bit likely. If it starts bad it finishes bad. On the contrary: no, just because the first 3 shots are close together and the velocity spread is low doesn’t mean it’s not going to get worse. Groups normally get bigger and velocities get wider, but, we have to start somewhere. It’s a matter of degrees. Also, the quality (accuracy) of the meter factors, and the better it is the better you can judge performance over fewer examples. And this is new brass, so that’s going to minimize inconsistencies further.

I can also tell you that it’s possible to wear out a barrel testing. No kidding.

Back to the “incremental” part of this test: As you increase the charges, bullets impact higher and higher on the target paper. You’re looking for a point where both group sizes and impact levels are very close together. If the groups are small, you won! That’s what Crieghton called a “sweet-spot” load, and that was one that didn’t show much on-target variance over a 2-3 increment charge difference (which is going to be about a half-grain of propellant). The value of such a load is immense, especially to a competitive shooter. It means that the daily variations, especially temperature, and even the small variances in propellant charges that might come with some propellants through meters, won’t affect your score. It’s also valuable to a hunter who’s planning to travel.

audette method loading
Audette Method: If it would only always work this way… This actually did work as shown so I captured and recreated it for posterity. The numbers on the left represent approximate propellant charge weights and the lines each indicate one click on my Harrell’s powder meter, a value about 0.15 grains of the propellant used in this test. Going up two clicks at a time for eight tries took me from 24.0 grains to about 26.0, which is a good range from a reasonable starting charge to pressure symptoms. I didn’t add in the velocities since that’s inconsequential to this illustration, but will say that “8” was too much and I settled on “6.” To make more sense out of this illustration, that ended up being 25.5 grains — step 6. I also went up using three rounds and skipping ahead by adding more clicks to the meter after viewing the (low) speeds on the first three groups (that’s why there’s no number 4 step; I went from step 3 to step 5). This has a lot to do with intuition sometimes. Point is, and should be, that here’s how the “Audette Method” is supposed to work: impact elevation on target goes up (these were fired at 300 yards) with charge increases, groups get smaller (hovering around two inches for this test) and stay small, and then elevation begins to stabilize. Choose a load that’s within this range. Then it’s a “sweet-spot” load. If this happens in your test, ask for no more!

That was the whole point to following this process. First, and foremost, it’s to find a good-performing load. It’s also how you find out if the propellant you chose is going to produce predictably. I can also tell you that I have chosen a propellant and a load using it that wasn’t always the highest speed or even the smallest single group. It was chosen because it will shoot predictably all year long. I base everything on the worst group, biggest velocity spread, not the smallest and lowest. If that doesn’t make sense it will after a summer on a tournament tour. If the worst group my combination will shoot is x-ring, and the worst spread is under 10 fps, it’s not the ammo that will lose the match…

As said to start this series, I started loading at the range because I got tired of bringing home partial batches of loser loads. And, you guessed it, the partial boxes usually contained recipes that were too hot. The only way to salvage those was to pull the bullets. Tedious. Or they were too low, of course, and fit only for busting up dirt clods. Plus, I’m able to test different charges in the same conditions. It’s a small investment that’s a huge time-saver.

If you do invest in a portable setup, exploit potentials. The possibilities for other tests are wide open, seating depth experiments, for instance.

CHECK OUT MORE TARGETS AT MIDSOUTH HERE

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: 3 Helps For Easy Load Work-Ups

Facebooktwittergoogle_pluspinterestyoutube

Read this before you start the process of working up a load for your new rifle! It could save you huge amounts of time and money… Find out more!

Glen Zediker

Spring is around the corner. Well, if you walk way out into the street and squint really hard you can at least think you see it… Well it’s coming soon enough, at least, now’s a good time to get ready.

I never have been big on the personal value of published load data. The data I’m referring to is that from propellant and other component manufacturers, and also from articles done by independents. I think all such information, at most, provides a place to start, and it also gives some ideas on tendencies and cautions, and provides means for comparisons. But. I don’t think it can be taken straight to the loading bench with any guarantee of success, or of attaining “advertised” performance. And I say that not because I don’t think these folks don’t know what they’re doing. They do! It’s because, after way more than enough experience in proving myself right, I can tell you absolutely that their rifle is not your rifle! Neither, necessarily, are their propellant, primer, case, or bullet. Always take careful note of the barrel and components used for any published test data, and compare them to yours. In later comparisons of my notes with published data, sometimes I’m higher, often times I’m lower, and enough times I’m way lower… That’s the main concern there.

It’s not at all difficult to learn to develop your own loads, to essentially write your own loading manual.

To do this efficiently, you need to learn to load at the range. Right, right there near to where you’re testing. An unremarkable investment in a few tools and a little creativity can provide a way to take your show on the road.

Lee press mounted outdoors
You don’t have to invest a fortune to take your show on the road. A C-clamp and one of these little Lee Reloader presses is all you need! And a good powder meter. One with a clamp is handiest, or just mount it to a piece of wood and clamp that down (even a pickup tailgate works just fine). One clamp is adequate on the press since bullet seating is all in the “down” direction and not much force is needed.

The reason to do this is because it provides a way to precisely chart results. It’s a more reliable and accurate way to proceed. Otherwise, the option is to load varying charges at home and then see what happens at the range. That’s okay, but not nearly as good as on-the-spot experiements. Plus, you won’t have left over partial boxes of poor-performing rounds. It’s more economical and way on more efficient.

The preparation part, and this is what you might spend the remaining cold month or two working on, is, first, to get the tooling ready and, second, and most important, to start making notes on your powder meter.

Important: To be able to work up at the range, it’s mandatory that you’re using a meter that has incremental adjustment. Either a “click”-type “Culver”-style insert or, at minimum, a micrometer-style metering arm. You’ll be relying on the meter, not scales, to progress upward in propellant charges, and you absolutely have to know what the values are for each increment using the different propellants you plan to test. That is where you’ll be spending time prior to doing your homework. It’s well worth it! It can be a nightmare trying to get scales to read accurately outdoors, including the digital type.

Harrells meter mounted outdoors
I map out the incremental values of each click on my Harrell’s meter adjustment drum with the propellant I’ll be testing, and it’s really easy to step up each trial with confidence. I carry the whole kit in a large tool box.
Harrells meter close up
This is a Culver insert. It’s a huge help in following this process. It’s precise and repeatable.

Equipment List and Set-Up
When I need to do load work, I size, prep, and prime new cases and put them in a cartridge carrier (usually a 100-round box). I then pack up my little press, seating die, my meter, some cleaning gear, C-clamps, and my propellants. The press and meter and cleaning gear go in a tool box. I usually carry the propellants in a picnic-type cooler. And, very importantly, my chronograph. A notebook, some masking tape, and a sack lunch… I might be there a while.

Always (always) use new cases for load work-up.

When I get to the range, I’ll clamp-mount my press and meter to a bench, get out all the rest, and set up the chronograph. Take a target downrange and tack it up. I test at 300 yards, unless the load is intended for shorter-range use. I initially test longer-range loads at 300. Maybe I’m lazy, but longer-range testing is a tad amount more tedious. I’ll come back for that after I have a contender or two.

Working Up The Load:
The reason it’s a “work-up” is clear enough: we’re almost always looking to get the highest velocity we can, safely. High velocity, or higher velocity, is usually all-good. Shorter flight time means less bullet drift and drop, and a harder hit.

So working up means increasing propellant charge until we’re happy: happy with the speed and also that the cases will still hold water. (And more about that next time…)

blown primer
Keep track of the cases in the order they were fired. This helps later on when the effects can be measured. This little outing here, though, didn’t require a gage to cipher: a tad amount hot on that last little go around (last case bottom row on the right). Thing is, I didn’t load a whole boxfull of those chamber bombs to take with me, and that’s the beauty of loading right at the range.

Very important: it is vitally necessary to have established a goal, a stopping point, prior to testing. That is one of the functions of published data. That goal is bound to be velocity, not charge weight. And that, right there, is why you’re working up at the range: you want to get “advertised” velocity and need to find the charge weight that produces it.

I work up 0.20 grains at a time. Sometimes it’s more if I’m reading an unuseably low velocity on the initial trial. Since my meter has a “Culver”-style insert, which I trust completely, I reference its number of clicks in my notes rather than the grain-weights (a Culver works like a sight knob, and reads in the number of clicks, not the weight itself). I check the weights when I get back, and I do that by clicking to the settings I found delivered, and then weighing the resultant charges. Otherwise, just throw a charge into a case and cap it with masking tape (clearly labeled).

It’s not necessary to fire many rounds per increment. “Mathematically” 3-5 rounds is a stable enough base to reckon the performance of one step. Of course, I’ll be shooting more successive proofs-per-trial once I get it close. Some folks, and especially competitive shooters, wear out a barrel testing loads. That’s not necessary.

Here are 3 things I’ve found over the years to better ensure reliable results. Learned, of course, the hard way.

1. Limit testing to no more than one variable. I test one propellant at a time, per trip. If you want to test more than one on one day, bring the bore cleaning kit and use it between propellant changes. Results are corrupt if you’re “mixing” residues. Same goes for bullets. Otherwise, though, don’t clean the barrel during the test. I fire my most important rounds after 60+ rounds have gone through it, so I want a realistic evaluation of accuracy and velocity.

2. Replace the cases back into the container in the order they were fired. This allows for accurate post-test measurements. Use masking tape and staggered rows to label and identify the steps. I use 100-round ammo boxes because they leave enough space for the tape strips.

3. Go up 0.20 grains but come off 0.50 grains! If a load EVER shows a pressure sign, even just one round, come off 0.50 grains, not 0.10 or 0.20. Believe me on this one…

Check out chronographs HERE
Take a look at suitable meters HERE

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: Neck-Only Case Sizing

Facebooktwittergoogle_pluspinterestyoutube

Neck-only resizing is an option for the bolt-action owner. Here are some ideas on why it works, and when it works best… Keep reading!

winchester bolt action
Neck-only sizing is for bolt-actions ONLY.

Glen Zediker

Cartridge case re-sizing is one of those topics that draws lines and forms camps. I am a big believer in full-length sizing, for any action type or use, and just saying that immediately draws argument.

Before getting into the “whens” and “whys” respecting full-length or neck-only sizing, here’s one that I think is an absolute: cases for reuse in a (any) semi-automatic should be full-length sized; neck-only sizing is only for bolt-actions. Having established that, all this next really only relates to what’s possible with a bolt-gun.

Backing up a bit: a “full-length” sizing die is one that returns the cartridge case body (and shoulder, if adjusted to do so) to near-to-new dimensions. A “neck-only” sizing die doesn’t touch the case body (and may or may not be able to touch the case shoulder). A full-length sizer also sizes the case neck, and, normally, the entire height of the case neck cylinder. A neck-only die can be adjusted to contact the height of the neck cylinder in various amounts.

hornady neck sizer
A neck-only sizing die doesn’t touch the case body, so there’s no reduction in case body diameter. This die can be adjusted to contact the case shoulder, and setting back the shoulder may still be necessary. Make sure you check cartridge case headspace!

The idea behind a neck-only die is to preserve fired case dimensions: make the case a closer mirror of rifle chamber dimensions. One advantage of neck-only sizing comes to those who expect, or need, to get a good many loadings from their cases, since this approach minimizes case stretching on subsequent firings.

However, the primary flag waved by neck-only fans says that it produces the best accuracy, and that full-length sizing is a compromise, favoring function over accuracy. I do and don’t agree, and the rest of this article I hope will clarify what I just said…

The reason I do and don’t agree is that I know folks who cannot get a good group unless they neck-only size, and I know other folks, and I’m one of them, who get very small groups following what many would say is “over-sizing” their cases.

forster neck sizing set
Here’s a nice set for neck-only sizing. The “bump” refers to the capacity to also contact the case shoulder to control its dimension, if wanted.

I believe that the main influence in realizing the virtues of neck-only sizing has a whopping lot to do with the rifle chamber. Specifically, factory-made, off-the-shelf bolt-actions tend to have relatively more generous chamber dimensions, as will many older surplus-sourced rifles. “More generous” is in reference to the tolerances established for the SAAMI blueprint for the cartridge. This is (wisely) done to help ensure that any and all factory ammo will chamber and fire, and also to help ensure general and all-around feeding reliability. Additionally, it’s common to find some (slightly) oval chambers in factory guns; that has a lot to do with the freshness of the tooling when that chamber was cut. It’s even more common to find them that are off-center.

Purpose-built bolt-action competition rifles, such as those constructed for use in NRA High Power Rifle competition, are custom-chambered* and, while few will use what we might call a “tight” chamber, it’s not likely to encounter one on the larger end of acceptable dimensions.
*”Custom,” here, doesn’t mean they are each unique, it just means that they are done by hand employing a precision-made reamer and therefore are what they ought to be, or we sure hope so. And they don’t tend to be overly generous in (any) dimensions.

neck sizing bushings
If you’re going to go, go all in: dies with interchangeable bushings let you control case neck diameter, adding another measure of control, and even less working and re-working of the brass.

So, in the circumstance where we have a chamber that’s a tad amount big and a cartridge case that’s been manufactured to (usually) the smaller end of SAAMI-set standards, that case will endure more expansion, in all directions, than if it had been in a tighter chamber. Sizing only the case neck to accept and retain another bullet, as said, reduces the subsequent expansion that will occur the next firing, but also, and this is likely if there is an accuracy improvement, the otherwise un-sized case might then be sitting more centered in the chamber. And one reason for that is, if the rifle is equipped with a plunger-style ejector (Remington 700 style) that will bear against one edge of the head of the chambered round, pushing the cartridge off-center, askew. (This ultimately creates another undesirable condition, a warp in the case, and we’ll talk about that another time.)

So, a little bigger case returning to a little bigger chamber likely has a little better chance of getting centered, and I truly believe that is why neck-only sizing can be a help to accuracy for a bolt-action. However! A dimensionally-correct case returning to a dimensionally-correct chamber will perform just as well on target. Full-length sizing a case for reuse in a rifle with what I call a “standard” chamber (which is really running a little closer to the minimums established by SAAMI) also makes for good groups. We prove that every High Power Rifle tournament.

Advice: If you notice your bolt-action doesn’t shoot too well with factory loads, neck-only sizing should pay off and is well worth a try. Do, however, make sure to gauge the cases as is often discussed in Reloaders Corner, and, specifically, cartridge case headspace. If the bolt isn’t closing easily, that’s liable to be the culprit right there: shoulder has gotten too tall.

If you’re running a factory bolt-action, by all means try neck-only sizing. If you want to compare results to full-length sizing, just make sure you’re doing that operation right.

david tubb
Now. Don’t go getting the idea that full-length sizing can’t shoot well. Here’s a 1000-yard prone group at the hands of David Tubb, originator of the 6XC cartridge. Tubb sets case shoulders back 0.002 inches, runs 0.004 case neck tension, and full-length resizes using what amounts to a “small-base” die (additional 0.0005-inch reduction at the case head). He’s also not shooting a factory chamber. (Photo note: the yellow pasters were sighters; red pasters indicate record shots).

Check HERE and HERE to get started…

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.