Tag Archives: Handloading for Competition

RELOADERS CORNER: Barrel Throat Erosion

Facebooktwittergoogle_pluspinterestyoutube

How long does a barrel last? About 5 seconds. KEEP READING

throat erosion
Well, it’s hotter than this, but it’s flame cutting over time and distance, and hotter for longer is the issue.

Glen Zediker

As is by now common enough in this column I write, ideas for topics very often come from questions that are emailed to me. As always, I figure that if someone has a question they want answered, then others might also like to know the answer. This question was about barrel life and, specifically, this fellow had been reading some materials on the interweb posted by some misinformed folks on the topic of bullet bearing area and its influence on barrel life: “Is it true that using 110 gr. vs. a 150 gr. .308 bullet will extend barrel life because of its reduced bore contact?”

NO. Not because of that.

However! The answer is also YES, but here’s why…

Wear in a barrel is virtually all due to throat erosion. The throat is the area in a barrel that extends from the case neck area in the chamber to maybe 4 inches farther forward. Erosion is the result of flame-cutting, which is hot gas from propellant consumption eating into the surface of the barrel steel. Same as a torch. There is very little wear caused from passage of the bullet through the bore, from the “sides” of the bullet, from friction or abrasion. The eroding flame cutting is at or near the base of the bullet.

When the propellant is consumed and creates the flame, the burn is most intense closer to the cartridge case neck. There are a few influences respecting more or less effect from this flame cutting. Primarily, it’s bullet weight. Time is now the main factor in the effect of the flame cutting. Slower acceleration means a longer time for the more intense flame to do its damage.

The slower the bullet starts, and the slower it moves, the more flame cuts in a smaller area for a longer time.

Bullet bearing area, therefore, has an influence on erosion, but that’s because it relates to acceleration — greater area, more drag, slower to move.

The amount of propellant, and the propellant nature, do also influence rate of erosion. Some assume that since there’s more propellant behind a lighter bullet that would create more erosion, and that’s true, but that is also not as great a factor as bullet weight. Other things equal, clearly, more propellant is going to cut steel more than less propellant. A “lighter” load will have a decidedly good effect on barrel life.

throat erosion
It’s heavier bullets that have the most influence on shortening barrel life.

Heavier bullets, without a doubt, are a greater influence than any other single factor. “We” (NRA High Power Rifle shooters) always supposed that it was the number of rapid-fire strings we ran that ate up barrels the most, but that was until we started using heavier bullets and found out in short order that our barrels weren’t lasting as long. That was moving from a 70gr. to an 80gr. bullet.

The “nature” of propellant is a loose reference to the individual flame temperatures associated with different ones. There have been some claims of greater barrel life from various propellants, but, generally, a double-base will produce higher flame temperature.

Even barrel twist rate plays a role, and, again, it’s related to resistance to movement — slower start in acceleration. Same goes for coated bullets: they have less resistance and move farther sooner, reducing the flame effect just a little. And, folks, it’s always “just a little.” It adds up though.

There are bullet design factors that influence erosion. A steady diet of flat-base bullets will extend barrel life. There’s been a belief for years and years that boat-tail bullets increase the rate of erosion because of the way the angled area deflects-directs the flame. And that is true! However, it’s not a reason not to use boat-tails, just a statement. We use boat-tails because they fly better on down the pike, and, ultimately that’s a welcome trade for a few less rounds. An odd and uncommon, but available, design, the “rebated boat-tail” sort of splits the difference and will, indeed, shoot better longer (they also tend to shoot better after a barrel throat is near the end of its life).

The effects or influences of barrel throat erosion are numerous, but the one that hurts accuracy the most is the steel surface damage. It gets rough, and that abrades the bullet jacket. The throat area also gets longer, and that’s why it’s referred to as “pushing” the throat.

The roughness can’t much be done about. There are abrasive treatments out there and I’ve had good luck with them. Abrasive coated bullets run through after each few hundred rounds can help to smooth the roughness, but then these also contribute their share to accelerated wear. I guess then it’s not so much a long life issue, but a quality of life issue. I do use these on my competition rifles.

lnl gage
Use the Hornady LNL O.A.L. gage to record and then track barrel throat wear. This isn’t technically a “throat erosion gage,” which do exist, but I’ve found it an easy and reliable way to keep up with an advancing throat. As the seating depth gets longer, it’s indicating how far the throat is advancing. Get one HERE 

Keeping in mind that the throat lengthens as erosion continues, using something like the Hornady LNL tool shown often in these pages can let bullet seating depth that touches the lands serve as a pretty good gage to determine the progress of erosion. On my race guns, I’ll pull the barrel when it’s +0.150 greater than it was new. Some say that’s excessively soon, and a commonly given figure from others in my circle is +0.250. One reason I pull sooner is that I notice a fall-off in accuracy sooner than that since I’m bound by a box magazine length for my overall cartridge length for magazine-fed rounds with shorter bullets, and I’m already starting with a fairly long throat (“Wylde” chamber cut). And another is because gas port erosion is having some effect on the bullet also by that number of rounds. Which now leads into the “big” question.

So, then, how long does a barrel last? Get out a calculator and multiply how many rounds you get before pulling a barrel by how long each bullet is in the barrel and barrels don’t really last very long at all! At full burn, maybe 4-6 seconds, some less, or a little more.

Another misgiven “fact” I see running rampant is associated with comparing stainless steel to chromemoly steel barrels for longevity. Stainless steel barrels will, yes, shoot their best for more rounds, but, chromemoly will shoot better for an overall longer time. Lemmeesplain: the difference is in the nature of the flame cutting effect on these two steels. Stainless tends to form cracks, looking like a dried up lakebed, while chromemoly tends to just get rough, like sandpaper. The cracks provide a little smoother surface for the bullet to run on (until they turn into something tantamount to a cheese grater). The thing is that when stainless stops shooting well it stops just like that. So, stainless will go another 10 to 15 percent more x-ring rounds, but chromemoly is liable to stay in the 10-ring at least that much longer than stainless steel.

throat erosion
Stainless steel barrels keep their “gilt-edge” accuracy for about 15% more rounds, but hit the wall head-on and in a big way when they reach their limit. Chromemoly steel tends to open up groups sooner, but also maintains “decent” accuracy for a longer time, by my experience — the groups open more slowly.

Do barrel coatings have an effect? Some. A little. I’ve yet to see one that made a significant difference, or at least commensurate with its extra expense. Chrome-lined barrels do, yes, tend to last longer (harder surface), but they also tend not to shoot as well, ever. Steel hardness factors, but most match barrels are made from pretty much the same stuff.

The preceding is a specially-adapted excerpt from Glen’s book Top-Grade Ammo. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

RELOADERS CORNER: Making Space

Facebooktwittergoogle_pluspinterestyoutube

Some reloading ops don’t have to be done in a full-blown shop. Here are a few ideas when space, and comfort, are both at a premium. READ MORE

home reloading
There are stand-alone and then set-aside mounting solutions for folks who don’t have shop space. This is from Lee and available here at Midsouth.

Glen Zediker

I recently, at his request, took on the task of teaching one son to reload for his AR15. It was in the middle of the winter and my shop/studio area was pretty much closed down for the season. But he persisted, and it was also just the sort of thing I needed to shift gears and give myself a test of what I truly do know that I set out to share with you all each edition. I say that sort of humorously, but not really! Getting back to the basics, starting from the start, is a great idea. I recollect from experiences in what amounted to another life for me (I used to be a PGA Member), the great golf champion Jack Nicklaus would return to his original teacher, Jack Grout, at the start of each PGA Tour season and say: “I’m Jack Nicklaus. I’ve been thinking about taking up golf. Can you show me how to hold the club?”

So the immediate challenge for me was to make this learning experience worthwhile and also comfortable! And easy given the busy schedules we both have.

Many of us have well thought out and lavishly equipped reloading work spaces, and, others, not so much. All during the many many years I’ve been reloading, I’ve lived in apartments, moved to new locations, and, either way, didn’t always have access to the well-lit and sturdily-constructed “loading bench.”

I’ve made do, and, looking back, I don’t think I ever missed a point as a result.

Tricks and Tips
C-clamps are wonderful allies! Mounting many tools doesn’t require direct bench-top fastening. For years, even with a full-scale shop to stretch out in, I have been a fan of mounting tools on “platforms” and then clamping that to the bench when needed. I have a penchant for efficiency in loading and a big part of satisfying that is being able to relocate tools. In other words, I don’t want to have a trimmer, priming tool, and so on and on, all mounted in a (long) row along my benchtop. I want to be able to locate them where I want them, when I need them.

home reloading
A little creativity can mount most tools for easy location-relocation. Drill straight! That matters.
home reloading
Here’s a Forster trimmer mounted to that wood piece that can pretty much clamp anywhere.

Get to the hardware store and invest in some wood pieces, fastener-fixtures, and hex-head-screws. Take a priming tool, for instance, and mount it to the wood and then clamp that to the benchtop (or any suitable surface, anywhere) and commence to using it. Simple!

home reloading
This is an easy way to mount a quickly removable tool, like this small Lee press.

I’ve also had good success locating the tool mount spots I prefer for various appliances on my benchtop and then using the hex-head screws to attach the tools via installed threaded fastener receptacles when I want to use them.

home reloading
Built-in clamps are where it’s at. I’m a big fan of Harrell’s Precision tools and the omnipresent clamp is one small reason why.

I’ve even taken to doing that in mounting big tools. The bench where I load ammo is also the same bench where I build guns, or they share common area. After getting tired of bolting and unbolting vises and presses, I mounted each to a 2X12 piece of wood and affix either to the benchtop using a couple of honking c-clamps. As long as there’s enough area to get a good clamp down and enough surface area to sit the bench, I cannot tell the difference.

Now, when it comes to some higher weight and higher leverage tools, like presses, some of what you can get away with, in a way of looking at it, has a lot to do with how sturdy the base platform needs to be. Sizing .223 Rem.? Not much stress. Bigger cases, more stubborn ops, might need more substantial grounding.

For us, a combination of c-clamps and factory-mounted clamps on some of our meters and presses meant we could set up alongside each other at, believe it or not, our kitchen table and load in comfort, and easy access to a refrigerator!

home reloading
An assortment of fasteners: t-bolts and barrel screws from a hardware store, along with a c-clamp.

There are also some handy ready-made bases for loading available HERE at Midsouth.

Point is, if you don’t have access to a conventional bench, work area, or you want to prime cases while you’re watching television with your friends or family, there’s a solution. It just takes a little creativity.

Just pay attention to the loading!

home reloading
Here’s son Charlie ready to learn how to set up a sizing die… In the comfort of our kitchen, in the middle of the winter. Ammo loaded here shoots just as well as that done in the shop.

The preceding is a specially-adapted excerpt from Glen’s book Top-Grade Ammo. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

RELOADERS CORNER: Standard Deviation

Facebooktwittergoogle_pluspinterestyoutube

Before getting into improving bullet velocity Standard Deviation, it’s first necessary to understand what it is, and what it isn’t. KEEP READING

chronograph screen

Glen Zediker

I got started on this topic last time, and kind of came in through the side door. Quick backstory: the topic was how to start on solving unsuitably high shot-to-shot velocity inconsistencies. This time we’ll start at the other end of this, and that is taking steps to improve already suitable velocity deviation figures.

Clearly, the first step in getting involved in velocity studies is getting the velocities to study. Of course, that means you need a chronograph. Midsouth Shooters has a selection and there’s a direct link in this article.

Virtually all chronographs are going to be accurate. A well-known manufacturer of shooting-industry electronics once told me that unless a chronograph displays a reading that’s just crazy unrealistic, you can rely on the number. The reason is that the current state of circuitry is pretty well understood and heavily shared. Pay attention, though, to setting up the device according to suggestions in the instructions that will accompany the new chronograph. The more recent Doppler-radar-based units are not technically chronographs, but they function as such. The advantages to those are many! More in another article soon. For now, for here, what matters is getting some numbers.

labradar
Latest and greatest, in my mind, advancement in data collection is doppler radar based units, like this from LabRadar. Easy to use, and not finicky about sunlight and setup.

Point of all that was this: You don’t have to spend up for the best to get a good chronograph. One of the price-point differences in chronographs is how much it will help work with the data it gathers. Most of us any more don’t have to do hands-on calculations. Me? All I want is a number. However, there are a good many that will record, calculate, and print.

magnetospeed
Barrel-mounted electro-magnetic chronographs like this one from MagnetoSpeed make it easy. I like being able to read speeds without all the setup, and not having to rely on a benchrest-type restriction. It stays on the rifle so can easily be used in the field. There are rail mounts available also.

Terms and Twists
Speaking of calculations, the most known and probably most used expressed calculation of collected velocity figures is Standard Deviation. SD suggests or reflects the anticipated consistency of bullet velocities (calculated from some number of recorded velocities). “Standard” reflects on a sort of an average of the rounds tested. I know saying “sort of” disturbs folks like my math-major son so here’s more: SD is the square root of the mean of the squares of the deviations.

Standard Deviation calculations did not originate from ballistic research. It’s from statistical analysis and can be applied to a huge number of topics, like population behavior. SD calculation forms a bell curve, familiar to anyone who ever had to take a dreaded Statistics class. 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.

Calculating SD
If you have no electronic gadgetry to help: add up all the recorded velocities and divide them by the number of records to get a “mean.” Then subtract that mean value from each single velocity recorded to get a “deviation” from the mean. Then square each of those. Squaring them eliminates any negative numbers that might result from cancelling out and returning a “0.” Add the squares together and find the mean of the squares by dividing again by the number of numbers — minus 1 (divide by n -1; that eliminates a bias toward a misleadingly small result). Then find the square root of that and that’s the Standard Deviation figure, which is “a” Standard Deviation, by the way, not the Standard Deviation.

bell curve
This is a bell curve such as results from plotting an SD calculation, and is given here only an example of how the distribution, the “odds,” graph out.

Knowing a load’s SD allows us to estimate-anticipate how likely it is for “outliers” to show up as we’re shooting one round after another. Based on the distribution based on the curve, if we have an SD of 12, for instance, then a little better than 2 out of 3 shots will be at or closer to the mean than 12 feet per second (fps). The other shots will deviate farther: about 9 out of 10 will be 19 fps, or less, from the mean. 21 out of 22 will be 24 fps closer to the mean. Those numbers represent about 1.00, 1.65, and 2.00 standard deviations.

Now. All that may have ranged from really boring to somewhat helpful, to, at the least, I hope informative.

Mastery of SD calculation and understanding doesn’t necessarily mean smaller groups. It gives a way to, mostly and above all else, tell us, one, the potential of the ammo to deliver consistent elevation impacts, and, two, reflects on both how well we’re doing our job in assembling the ammo and the suitability of our component combination.

I honestly pay zero attention to SD. I go on two other terms, two other numbers. One is “range,” which is the lowest and highest speeds recorded in a session. The one that really matters to me, though, is “extreme spread.” That, misleading on the front end, is defined as the difference between this shot and the next shot, and then that shot and the next shot, and so on. Why? Because that’s how I shoot tournament rounds! This one, then another, and then another. A low extreme spread means that the accuracy of my judgment of my wind call has some support.

Depending on the number of shots and more, SD can be misleading because it gets a little smaller with greater amounts of input. Extreme spread doesn’t. I have yet to calculate an SD that put its single figure greater than my extreme spread records.

Lemmeesplain: The shot-to-shot routine is to fire a round. It’s either centered or not. If it’s not centered, calculate the amount of correction to get the next one to center. Put that on the sight. Fire again. If I know that there’s no more than 10 fps between those rounds, that’s no enough to account for (technically it can’t be accounted for with a 1/4-MOA sight) then it’s all on me, and if it’s all on me I know that the input I got from the last shot, applied to the next shot, will be telling. Was I right or wrong? It can’t be the ammo, folks. Then I know better whether the correction is true and correct.

Some might be thinking “what’s the difference?” and it’s small, and so are scoring lines.

A load that calculates to a low SD is not automatically going to group small, just because it has a low SD. Champion Benchrest competitors have told me that their best groups don’t always come with a low-SD load. But that does not apply to shooting greater distance! A bullet’s time of flight and speed loss are both so relatively small at 100 yards that any reasonable variation in bullet velocities (even a 20 SD) isn’t going to open a group, not even the miniscule clusters it takes to be competitive in that sport. On downrange, though, it really starts to matter.

For an example from my notes: Sierra 190gr .308 MatchKing, in a .308 Win. Its 2600 fps muzzle velocity becomes 2450 at 100 yards and 1750 at 600 yards (I rounded these numbers).

If we’re working with a horrid 100 fps muzzle velocity change, that means one bullet could lauch at 2550 and the next might hit 2650, in the extreme. The first drifts about 28 inches (let’s make it a constant full-value 10-mph wind again to keep it simple) and the faster one slides 26 inches. That’s not a huge deal. However! Drop — that is THE factor, and here’s where inconsistent velocities really hurt. With that 190, drop amount differences over a 100 fps range are about 3 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 is going to cost on target. And it gets 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).

This 100 fps example is completely extreme, but half of that, or even a quarter of that, still blows up a score, or creates a miss on an important target.

That all led to this: What is a tolerable SD?

I say 12. There has been much (a huge amount) of calculation that led to that answer. But that’s what I say is the SD that “doesn’t matter” to accuracy. It’s more than I’ll accept for a tournament load, but for those I’m looking for an extreme spread less than 10 fps (the range might be higher, but now we’re just talking terms). More later…

Check out chronographs HERE

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

RELOADERS CORNER: Velocity Consistency, Part One

Facebooktwittergoogle_pluspinterestyoutube

Shot-to-shot muzzle velocity consistency is almost always a high-ranking goal for the handloader. But what about when it’s just awful? READ MORE

chronograph display

Glen Zediker

Last edition the topic was a wide-scope look at propellants, and the underlying point was how to get started, how to choose one. There’s not a perfect answer to that, or not one I can warrant as absolutely decisive.

Propellant choice often comes down to experience (good and bad), and that’s one reason that many of us, and me most definitely, tend to stick with a few, and those also are the first we’ll try when starting up with a new project. It’s also one reason we might be hesitant to try a propellant again if it didn’t work well the last time. I have those hesitations.

There are also criteria that we’d all like to have met, and, as also said last time, sometimes those have to be ranked or weighted. We may not find the maximum velocity with the smallest group size with one propellant, and, for me, group size gets the most weight. That’s why I said that the best choice is often the one with the fewest compromises, and that’s assuming there’s likely to be some compromise, somewhere. And that’s a fair and wise assumption.

One criteria that I and others have pretty high on our lists is velocity consistency. One measure of a “good load” is low variations in measured muzzle velocities. This, without a doubt, is of more importance the more distant the target.

The propellant that tested showing the lowest shot-to-shot velocity deviation does not necessarily mean that load combination is going to be the most accurate. One reason it’s important might not only to do with on-target accuracy as it does with providing clues about either the handloading protocols we’re following or the suitability of the component combination we’re using.

This article will focus more on that last — suitability of the component combination — and more to follow later will be dedicated to the performance component of consistent velocities.

I got a letter just before doing this article asking about reasons for seeing high velocity deviations. This fellow, a loyal reader of my books, was using the same component combinations and tooling advice I take myself and also publish, and not getting good results. As a matter of fact, his results were horrid. He was seeing deviations, shot-to-shot, in the vicinity of 100 feet per second (fps), plus. That’s huge.

After much time spent testing all this to collect enough notebook entries to think I have some handle on it, a half grain (0.50 gr.) of propellant in most small- to medium-capacity cases (say from .223 Rem. to .308 Win.) is worth about 40 fps. Given that, 100 fps difference is not likely to come from a propellant charge level variance.

Another reader posted a comment-question last article here regarding how to know if aged components were still good, still performing as they should, and this is a place to start looking if we’re seeing radical inconsistencies.

Two questions at the same time, as I’ve said before, usually point me toward a topic.

Moisture is the enemy in propellant and primer storage. The “cool dry place” is hard to come by, around these parts anyhow. I’ve had propellant go bad after having been stored in resealed containers. So far, I haven’t had any lose its potency after many years of storage in the factory-sealed containers.

“Go bad” can mean at a couple of things, by the way. One is that the propellant ages to the point that it changes. If propellant “spoils” it smells bad! It will have an acrid aroma. Don’t use it. Another way it goes bad is pretty easy to tell: it clumps. That is too much moisture. Don’t use it. Put it out in the garden, it’s a great fertilizer — honest.

Primers? It’s hard to tell… Bad primers still appear good.

My letter-writer’s huge velocity deviations were solved by a change of primer, and, mostly, a box of fresh primers. I kind of knew that was the component-culprit because he was having the same results or effects from different propellants.

Primers should be stored in air-tight containers, which will be something other than the factory packaging. Primers are “sealed” but that’s a lightweight assurance. Touching them, for instance, won’t hurt them, contrary to rumors, but more prolonged exposure to excessive moisture can and will take a toll, and its effects are very likely to be as inconsistent as the performance of the compromised primers.

Another strong caution: Always remove, or never leave, however you prefer, propellant in a meter. After you’re done with the loading for the day, return it to its storage container and cap it back tightly. Same with primers. Any left over in the priming tube or tray should go back to safe storage. Clearly, this all has a lot to do with the environmental conditions of your loading-storage area.

Out of curiosity, I filled a case with some small-grained extruded propellant and left it sit out in my shop. It was clumped when I checked it next day (24 hours). I had to get a pipe cleaner (nearest handy tool) to get it all out of the case. I don’t store propellant or primers in my shop, and that’s the reason… Yes, we have some humidity in my part of the world.

Excluding those obvious issues, what makes some combinations produce higher or lower velocity consistencies takes some experimentation to improve (or give up on).

Sometimes (many times) this all seems more like art than science. It is science, of course, but it’s not tidy; it can’t always, or even often, be forecast.

I’ve seen the biggest effect from a primer brand change. I also, though, don’t swap primer brands around each time I do a load work up and the reason is that there are other attributes I need from a primer. Since I’m loading nearly always for a semi-auto, an AR15 specifically, I have to use a “tough” primer, and that also means one that will accept near-max pressure without incident.

Point is that if you’re running a rifle/ammo combination that isn’t limited by either propellant choice or primer choice, you might very well see some influential improvements by trying a different primer (after getting the propellant decided on). Do, always, reduce the charge at least a half grain before using a different primer brand — primer choices also decidedly influence velocity and pressure levels. Again, in my experience, more than you might imagine.

Next time, more about the performance component of consistent velocities, and a whopping lot more about how to improve that.

Check Midsouth storage solutions HERE

The preceding is a specially-adapted excerpt from Glen’s book Top-Grade Ammo. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

RELOADERS CORNER: Bullet Seating Depth

Facebooktwittergoogle_pluspinterestyoutube

A popular topic in these pages, and for good reason: it can make a big difference in rifle accuracy! Read more about it HERE

benchrest bullets
Pretty much all bullets respond to seating depth changes. Long or short, for maximum accuracy it’s worth the effort.

Glen Zediker

Every time I do an article here in Reloaders Corner on the topic of bullet seating, I always see at least a couple of comments from readers about their experience and preferences with bullet seating depth. Those usually involve or revolve around seating a bullet so it is touching, or is nearly touching, the lands or rifling when the round is chambered.

This is a long-standing “trick” well known in precision shooting circles, like those competing in NRA Long Range or Benchrest.

Seeing What You’ve Got
First step, absolutely, is determining what the bullet seating figure is for your particular bullet in your particular chamber. This length is most often referred to as “dead length.” That’s a pretty ominous-sounding term! It’s not really perilous, but there is a little danger involved, which, mostly, is one point to respect. That point is that when a bullet goes from just off to just on — actually touching the lands — pressure will (not may) increase. Reason is that the previous gap-valve effect closed so burning gases are effectively “plugged up” a fractional millisecond longer. My experience with the most common small- to medium-capacity cases we’re using (ranging from, say, .223 Rem. to .308 Win.) is that this is worth about a half-grain (0.50-gr.) of propellant.

Finding It
Those who have read much in these pages have seen the Hornady LNL OAL tool. This is a well-designed appliance that will show you, in your chamber with your bullet, how far forward the lands are, or, more precisely, the overall cartridge length that will touch the lands. This amount varies and is unique! Don’t transfer figures from one gun to the next. It also changes… As the chamber throat erodes it lengthens, and so too will the overall cartridge length that touches the lands. Let’s call overall cartridge overall length COAL for sake of space.

hornady lnl gage
Here’s the tool to find the seating depth that touches the lands. Hornady LNL Oal Gage.

There are other means but I’ve not found one more accurate. Some smoke over a bullet that’s been seated into a “loosened” case neck and gauge contact by the marks left. This, however, is likely to be “touching, plus” length.

Once you’ve got the round ready to measure, I strongly suggest doing so using a bullet length comparator along with your caliper. This is another tool that’s been gone over and gone on about here. It measures at a point along the bullet ogive rather than on the bullet tip. It’s more accurate. Now. A comparator inside diameter is usually close to actual land diameter, but, as with chambers, these are each and both unique so don’t assume anything.

Hornady comparator
More precise reads come from using a bullet length comparator to measure overall length. This is a Hornady LNL too.

Why It Works
Setting the bullet so it touches the lands does a few things, all good. One, and I think one of the most influential, is that the bullet starts off aligned with the rifle bore. As a matter of fact, it better centers the whole cartridge because there is, not may be, at least a little gap between chamber and case. If there wasn’t the round wouldn’t enter the chamber. The bullet is, effectively, supported by the lands and that has, also effectively, taken up the “slack” by locating the cartridge more concentric with the chamber and bore. It also then effectively makes up for the affronts to concentricity created by case neck wall inconsistencies and the resultant relocation of the case neck center.

Another is that that it eliminates jump (the usual distance or gap between the first point of land diameter on the bullet nosecone and the lands). Bullet wizard Bill Davis (designer of the original “VLD” projectiles, and others of much significance) once told me that his thoughts on why especially the high-caliber-ogive high-ballistic-coefficient bullet designs worked best with no jump were for all those reasons and improvements just mentioned. Plus another: gravity. A bullet floating in space, and also moving forward in this space, has that much more opportunity to engage the lands at a little angle, if only because of gravity. Always have thought about that one.

Soft-Seating
There are degrees. When we go from just on to “in” that’s another tactic some experiment with. And it has another level that’s commonly popular with Benchrest and other precision shooters. That’s called “soft seating.” What that is, is setting the case neck inside diameter to very nearly match the bullet diameter with the idea that the bullet starts out extra-long and then chambering the round finishes the bullet seating when the bullet contacts the lands. The reason for the more generous case neck inside diameter is to reduce resistance so the bullet can more easily set back and let the lands seat it.

I don’t use this tactic, but have. It’s another level of commitment and, as is often true with such other levels, demands more attention and also limits utility. One is that it clearly is only for bolt-action use. Another is that it’s for single-shot use only; such rounds should not be loaded into a magazine or fed from a magazine. For another, once loaded the round can’t usually come back out. The bullet will stay and you’ll get an action full of propellant.

Seating Depth Experiments
Now this is a process I have used throughout. Most times I find that best accuracy comes with a seating depth that has the bullet “just” on the lands. Contact is made but it’s the same pressure level as if the bullet were sitting on the benchtop. I also often have found best group sizes come at a little less than touching, and, a few times, at a little more than touching. I’m talking about 0.002-0.003 longer than dead-length. Let’s call it “firmly touching” but also a long ways away from “jammed.” These rounds often can’t be extracted.

There’s an easy way to run seating depth experiments. Here’s how I do it: I load however-many rounds at dead-length plus 0.003 COAL. I load them all that way. I then take a small press I can clamp on to a benchtop or tailgate at the range, and install a micrometer-top seating die. For max accuracy, I already seated all these test rounds using this exact setup. Take along a caliper and comparator and a fresh notebook page. I’ve adjusted the propellant charge as said earlier by dropping it a tad. Now. I also know that there’s going to be a little difference in perfected results because of this because lengths that aren’t touching the lands are running 35-40 feet per second slower, but it still shows me what’s going to work best. If it ends up being a COAL with a little gap, I’ll bump it back up.

Last
As said, the COAL that works best is going to change because the throat is going to change. Check using the OAL gage and adjust. That means the load is also changing, a little bit, each time the bullet moves forward (more case volume), and that can affect zero and velocity.

It’s a lot to keep up with.

Another note: If you’re feeding these rounds from a magazine, and running them through a semi-auto match-rifle, make sure there is adequate bullet retention (difference between bullet diameter and case neck inside diameter, go good 0.003 inches). Don’t want the bullets jumping forward (inertia-induced). If, for example, you’re giving 0.002 hold-off, that little bit can get taken up easily and then, if the bullet gets on the lands, there’s a pressure spike.

GAGES, on sale now at Midsouth!

The preceding is a specially-adapted excerpt from Glen’s book Handloading For Competition. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

 

RELOADERS CORNER: Understanding Ballistic Coefficient

Facebooktwittergoogle_pluspinterestyoutube

Math and myth both get involved in bullet Ballistic Coefficient discussions. Keep reading to separate the two and learn exactly what BC is, and what it isn’t. MORE

bc

Glen Zediker

Years ago I explained in great detail to a fellow here all about ballistic coefficient and how it was calculated and how it could be used and how it can change and so on, and he stopped me: “So you mean it’ll hit furtherer on up the hill…” That’s it.

A “ballistic coefficient,” or “BC,” is a number assigned to a bullet that suggests its aerodynamic performance.

That’s a key word, “suggests.” The main suggestion is how well this bullet will fly compared to that bullet, and the one with the higher BC ought to fly better. Fly better means less drop and drift, and those, factually, are a product of the higher-number BC. My best all-inclusive definition what a higher BC does for us: less speed lost over distance. Regardless of the muzzle velocity or the distance, one bullet with a higher BC will lose relatively less velocity over the same distance.

bullet blueprint
Here’s a blueprint. All the information needed to calculate a BC is contained here. It doesn’t have to be a real bullet because a BC model is not a real bullet either. Design factors that influence BC are virtually every design factor: length, ogive, boat-tail, meplat, weight. These factors, in this instance, calculate to a G1 BC of 0.560. By the way, there’s about a 5 point BC increase for each added 1 grain of bullet weight.

BC is calculated based on a standard bullet model. There are 7 of those. Two are normally used to determine BC for conventional rifle bullets, like what the most of us reading this use. Ballisticians and designers know which model to apply to different bullet types. The common model is a “G1” (another is 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 does not in fact exist. BCs are derived by comparison.

g1
The older standard for most rifle bullets was the G1. The newer, and better, standard is the G7. However! BC is never chiseled into stone regardless of the model. It’s a way to compare bullets, and a place to start figuring yours out.

g1 and g7

The standard bullet of any form-factor has a BC of 1.000. An actual bullet that’s compared to the model at points downrange will either be flying faster or slower than the model. If it’s moving faster, its BC will be greater than 1.000. If it’s going slower, it will be less than 1.000. It’s a percentage of the standard or model bullet’s performance.

Now. That is also all that it is!

BC is not an infallible factual statement about precisely what a bullet will be doing when it’s loaded and fired at that target than moment with that rifle. Not nearly, not hardly.

To me, BC gives us a place to start estimating drop (elevation) and also clues to how much it will get moved by a wind. It’s a way to compare bullets.

BC changes! Day to day, place to place, hour to hour.

Some bullet makers publish a BC for a bullet based on actual testing (chronographs) but now it’s pretty much “just math.” That’s fine. Which — math or measure — provides the best information? Some believe that a measured, tested BC is more realistic and, therefore, more valuable. But, if the point is to compare bullets, calculated BCs is more reliably accurate.

We (NRA High Power Rifle shooters) have gone to difficult and frustrating lengths to collect data to calculate “real” BCs (chronographing at 500+ yards hain’t always easy). Measured BCs are quite often lower, and they are quite often higher. Reasons follow.

The accuracy of drift and drop tables clearly revolves around what the actual, at that moment, BC performance is from the bullet you’re shooting (compared to what it’s “supposed” to be).

Anything that can influence bullet flight influences the actual, demonstrated BC performance.

BC uniformity is important. Bullets that show uniform BC performance produce less elevation dispersion. A source for variation is the meplat (bullet tip). Hollowpoint match bullets are notorious for inconsistency in this area. There’s a tool, a “meplat uniformer,” that fixes it. That’s pretty much the point to the plastic points on bullets like Hornady’s A-Max line.

Atmospherics, which add up as a list of factors, have a huge influence on BC performance. 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 stated BC as do any conditions that serve to disrupt its headway. BCs are based on sea-level so can easily show as a higher number at a higher elevation. I can tell you that bullets fired at The Whittington Center in New Mexico have a noticeably better BC than those shot at Port Clinton, Ohio.

Range 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.

Bullet stability is even 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 tested BC.

Factors that don’t matter in BC? Caliber. I’ve been argued at often over this next, but it is perfectly and absolutely true: BCs work the same regardless of caliber or bullet weight. Two bullets that each have a 0.550 BC, for instance, behave the same. That’s helpful, and at one time was more helpful than it is now. When we had to use paper tables to get drift and drop data and there was a new bullet that didn’t yet have those tables done, all you had to do was find data for another bullet with the same BC, go to the same muzzle velocity, and that data was 100-percent accurate. A .308 and .224 that both have the same BC share the same table. Remember, it’s not “real,” it’s a mathematical model.

So if you take a load to the target one day and you’re putting on more elevation than the BC-based calculation says you should, the BC isn’t wrong. The day is just different.

Finally, does it matter (really) if a bullet BC is based on a G1 or G7 model? Debates continue. But, not really, and I say that because BC is still only a suggestion. G7 is a more closely matched model to what we’re usually shooting when we think of a “high-BC” bullet, but all the same factors day to day also influence its accuracy. Given access to the data, I definitely, though, go with G7 calculations to have a place to start from. My experience has been that there is less difference in varying conditions, but, again, it’s still (plenty) enough change that you cannot dial it in and win anything…

The preceding is a specially-adapted excerpt from Glen’s book Handloading For Competition. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

RELOADERS CORNER: Case Trimmers

Facebooktwittergoogle_pluspinterestyoutube

An ideal case trimmer provides precision, speed, and affordability. Here are some ideas on avoiding compromise. READ MORE

Hornady Cam-Lok
Hornady Cam-Lock. Good trimmer at a fair price. See it HERE

Glen Zediker

At some point, or points, cases need to be trimmed to a shorter length. Brass flows. Therefore, a case trimmer is pretty much a given in the tool assortment for any handloader.

There are needs and wants, realities and ideals. That’s true with many things, and applies often to reloading equipment. Ideally, a case trimmer will go beyond just trimming the case to a shorter length. They all do that well enough. I think it’s important that a case has a square mouth — dead flat across the top. This is an asset to getting a bullet started well into the case neck during the seating operation.

A Good Trimmer
There are a variety of trimmers available from most of the popular industry tooling suppliers. And most follow a pretty similar form and formula: a little hand-cranked lathe. In these, the back end of the case is chucked into a collet-type fitting. A caliber-size pilot that’s centered in and surrounded by a cutting head goes into the case neck and supports the front of the case.

Not nearly perfect! There are a few reasons and sources for reduced precision. The tool alignment may be true at each “end” of the trimmer, but the case we’re working with probably isn’t true. Mostly, since there has to be a gap for the pilot to freely rotate, and since case neck walls aren’t all consistent in thickness, the fit isn’t close enough to prevent out-of-round rotation. Along with the inevitable case body warp there’s bound to be a tad amount of wiggle. Since the case is supported only at its head area, not by its body, there’s flex afoot.

None of that means the case neck won’t get trimmed to a shorter length, which is the general idea. It does, however, mean that it’s not liable to be perfectly squared up.

LE Wilson
LE Wilson. See it HERE at Midsouth.

A Better Trimmer
I rarely just overtly recommend one tool over all the others, but after a good many years working with case trimmers, I can and will tell you that the LE Wilson design is the best I’ve yet tried. I guess, yes, that is just opinion, but it’s really not.

The difference in this trimmer design is that the case is supported within a sleeve by its body. There’s no polarized suspension front and back. Mostly, there’s no pilot. The cutter on an LE Wilson faces off the front of the case squarely. The sleeve holding the case sit atop a pair of rails and the whole arrangement excludes case condition from the process.

le wilson sleeve
Tap it in… Then tap it out…

le wilson sleeve

So why doesn’t everyone use one? Honestly, I’m not entirely sure. It is a different arrangement, and it’s not cheap, especially not if you accessorize the fool out of it with a stand, a clamping device, and a micrometer. It’s not more than the other higher-end manual trimmers though.

It’s also fast! There’s no clamp-twisting to get the next case in place, and back out again. The sleeves are slightly tapered inside so the case is tapped in and then tapped out. With a little experience it’s amazingly quick to get through your block full of brass.

Flexibility
Virtually all case trimmers can provide additional utility, do different jobs. The cutter can be replaced with a reamer, and some can get reworked into outside case neck turners.

My choice is usually a stand-alone station, and that’s mostly because it’s pretty tedious refitting the appliances. I am, or at least have become, lazy.

forster case trimmer
Forster. This is a good choice especially for those who want to make a multi-purpose tool out of their base unit. There’s a big collection of add-ons that let work over primer pockets, turn case necks, ream case necks, and even hollow-point bullets. Its precision is better than most.
forster accessories
A a few of the things that can go on a Forster. Very versatile tool!

As with all said about alignment for case length trimming, that is also all the same for using a trimmer for other chores. And, yes, I still think the LE Wilson works best as a reamer, for instance, and that is because all the alignment precision is built into the tool itself; the case doesn’t play a role.

About options, by all means fit up a “combo-head” if it’s available that will finish the trim with a nice inside/outside chamfer/deburr. Big time saver. These can be a trick to get set just right, but it sure saves time.

Power
It sure is nice to get a break from the crank! There are, though, as I see it, two kinds of power case trimmers. Those that replace the hand crank with an electric motor and those that are designed from the start to be powered.

Some trimmers offer a means to add your own power source, like an electric screwdriver or drill.

Gracey Match Prep
Gracey Match Prep. Pretty much a big motor! It’s intimidating on first use, but just push the case in and it gets trimmed (and chamfered). It’s way quick in use and produces precise results.

My favorite proprietary power trimmer is a Gracey “Match Prep.” Designed by the late Doyle Gracey as a fast and easy way to trim huge quantities of Lake City brass for NRA High Power Rilfe shooters, it’s a serious machine. It works like a gigantic electric pencil sharpener, at least in spirit. Pick up a case and push it forward into a collar and it’s trimmed and squarely faced. No clamps or sleeves. The case shoulder stops against the inside of the collar, so it’s imperative that all cases are resized prior to use. As said last time, though, that’s really the only time you’ll get consistent results with any trimmer.

gracey holder
A key to a Gracey’s speed is that the cases stop on the case shoulder: just push it it!

I don’t know how many cases I can trim in an hour because I’ve never spent an hour using a Gracey. I can easily do 100 in under 5 minutes.

Another very good power trimmer is the Giraud. Its essential means for and in operation are about the same as Gracey but it is a nicer package with more features. Gracey is pretty daggone simple. That’s not all bad. I’d say Giraud is the best, and its price does reflect that.

One Last
Again, it’s important to evaluate the overall condition of a batch of cases, related to how many uses they’ve had. Having grown a little longer isn’t likely to be the only thing that’s changed in a case that exceeds whatever limit you set for it.

And, speaking of, the “trim-to” length is usually 0.010 inches shorter than the maximum SAAMI-stated overall case dimension.

Next time we’ll look at tools used to treat the trimmed case necks and finish this task in fine style.

Check out some more options at Midsouth HERE

Gracey
Giraud

The preceding is a specially-adapted excerpt from Glen’s book Top-Grade Ammo. Available HERE at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, and also free article downloads.

RELOADERS CORNER: Case Trimming

Facebooktwittergoogle_pluspinterestyoutube

We all have to trim bottleneck cases sometime. Question is when and how much, and then “how,” and here’s a place to start. KEEP READING

case trimmer

Glen Zediker

After going through that last series on keeping up with changes in cases resulting from their use and reuse, “flow” was a culprit behind the majority of detrimental changes. That is: Brass flows during firing. It moves from where it was to somewhere else. Since there’s a finite amount of material in a case, one place is getting thinner and another is getting thicker. The sources of the material, where the flow starts and where it stops, are primarily case necks and case heads.

To completely finish up on all this, the most obvious indication that there’s flow is measuring case lengths from base to mouth.

case trimming
The primary reason to trim is to keep overly-long cases from overrunning their space in the chamber. If the case mouth encounters the end of its allotted space, it can pinch in on the bullet, elevating pressure. Now, there’s usually a good deal of leeway before safety can be a question, but don’t push it…
measure case length
A caliper is the only tool needed to measure case length. It’s not really necessary to measure each and every case each and every time. It’s a whopping lot faster to set the trimmer so it just touches the shortest case you have (revealed through the process itself in setting up the trimmer) and trim all the cases using that setting locked in place.

First, and very (very) important: The ONLY time to check case length, or to trim cases, is after they have been sized! A fired, unsized case will be shorter than it was going in. The reason is because of the expansion in the case that resulted from firing. When the expanded areas are squeezed back to spec by a sizing die the case gets longer as it gets smaller in diameter, same as rolling a ball of modeling clay out on a table. After sizing is also the only time we can we know that the case shoulder area is consistent in dimension.

You’ll see two length figures published for your cartridge of choice: maximum length and trim-to length. Published trim-to length is usually 0.010-inches under what’s listed as maximum.

I got a gage umpteen years ago that could indicate the maximum case length a chamber could accommodate — technically, a “chamber length gage.” Man. I checked the chambers in my main rifles and found that they were all well more generous than the SAAMI-maximum. That didn’t really mean a lot, in fact, to how I proceeded. And it also didn’t mean I can advise ignoring the potential for danger in exceeding SAAMI-maximum. It just pointed out that there are differences in chambers, gun to gun, and at least showed me that not exceeding max stated length should easily keep you safe.

chamber length gage

If a case got too long, exceeded the amount of room given to it in the chamber, that would be a safety problem! The bolt may not close fully. And, if it did, the extra length would create a pinching-in constriction, and that would spike pressure.

We can easily imagine that there’s an influence from relatively longer or shorter case necks in their influence in consistently encasing the bullet. And I’m sure we’d be right. Trimming cases all the same should mean that all the case neck cylinders are the same height. Someone looking to maximize accuracy is liable to get worked up about that enough to trim each firing. I trimmed my tournament cases each use. And, no, none were remotely approaching maximum length. It’s reasonable to further suppose that more or less retention will influence velocity consistency.

Another performance asset may or may not happen, depending on the trimming tool chosen. But. A good trimmer will square the case mouth. I’ve seen a many new cases with a “half-moon” cut after trimming. A square case mouth helps a bullet start and finish straight when it’s seated.

case trimmer
Not all case trimmers are equal. We’ll talk more about some I like next time, and I’ll tell you why.

My routine for this sort of “accuracy-oriented” case trimming is simple — tedious, but simple. I don’t measure each case. I just run them all through a trimmer set to “some” length. Some are trimmed more or less, some just show a bright scuff on one little bit of the case mouth, but they are then all the same length. If I can’t prove it in group sizes, it sho does set my mind at ease that all the cases are holding all the bullets more nearly the same.

For those rifles that aren’t tournament guns, the only concern is that none, indeed, become too long. Those I will check at that “4-firings-in” point. Some may have reached SAAMI-maximum, most won’t have, but all will be longer than when started. I start them at a figure close to suggested “trim-to.” Stop and think about it, and if there’s been overall a 0.010-inch length increase, that’s significant.

As with all things associated with use and reuse in semi-autos compared to bolt-actions, cases are going to grow more and faster in a gas-gun.

Another instance where it’s important to keep up with case lengths, and that, again, really has to do with making them all the same, is for those who crimp (with a conventional cannelure method).

Now, there’s zero harm in using a longer “trim-to” length, and that may be more popular than my method. These lengths are stated in reloading manuals. Keeping up with it over years, I’ve seen no difference in the rate of lengthening trimming longer or shorter; I trim “shorter” solely as a matter of consistency over the (short) life of my semi-auto cases.

Next time more about the tools.

Get started shopping HERE

The preceding is a specially-adapted excerpt from Glen Zediker’s book Top-Grade Ammo.

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

Glen’s newest book, America’s Gun: The Practical AR15. Check it out HERE

par15

RELOADERS CORNER: Cartridge Evolution

Facebooktwittergoogle_pluspinterestyoutube

Here’s a short retrospect on what’s set the standards for most new cartridge designs, and why… KEEP READING

Glen Zediker

ppc

I’m not an engineer, but, like all of us, we rely on those folks to develop just about all the things we have and use. When we look at a new development, one that’s proven to work better than the “old” way, sometimes it’s easy enough to understand why. Cartridge development over the years is a good example.

What makes a good cartridge? Answers, of course, vary with the intended use, the performance needs. For the most part, power (which mostly is velocity), and “efficiency” (which is essentially getting the most from the least amount of propellant, likewise increasing barrel life), and accuracy (always) top the list. And, to me, “accuracy” is a combination of small group sizes and, even more, small group sizes all the time! Consistency.

Case capacity has the most to do with the first: more room for gunpowder means more power. Also, it’s pretty clear that pressures have been going up! There’s a big (big) difference in the pressure levels of some of the “new” cartridges compared to the older, longer-lived rounds. Sometimes it’s not because the older round can’t “take” the additional pressure, it’s because the guns might not. A round developed turn-of-the-century fits a rifle from the same era. Well, steel has improved, manufacturing has improved, and, some no doubt, is that the trend toward “shorter, fatter” cartridge cases also contributes.

So. About that…

In my mind, and certainly in my “world,” which is competitive shooting, one of the most influential cartridges has been, and still is, the PPC. That was developed in 1975 by Ferris Pendell and Dr. Lou Palmisano (hence “Pendell, Palmisano Cartridge”), and the idea was to design the “world’s most accurate cartridge.” They did. It has the record to prove it. However, that’s in Benchrest (capital “B” meaning formal competition). Bechrest is nearly always a 100-yard event. The idea behind the PPC wasn’t to set the range on fire with excessive velocity, although it’s well more rapid than others then popular in that game. The idea was to improve cartridge structure to improve shot-to-shot consistency, and another part of that plan was to extend the duration of load-to-load consistency by slowing down firing-induced changes to the case. It’s native caliber is 6mm (.243).

(By the way, the PPC is based on .220 Russian, which is still how many get their brass: fire form it from that. That round is associated with 7.62X39mm, which came earlier and was based on the WWII German 7.92x33mm Kurz, the Mittelpatrone.)

PPC and .223
PPC isn’t for everyone. It’s expensive and not nearly the fastest available today. However, it sho has had its influence on modern rounds. It’s expensive, by the way, because of the available brass: it’s from Lapua or Norma and has machined primer pockets, and other such points of perfection. Compared to .223 Rem. (right) which, in configuration, follows pretty well accepted architecture, similar to .30-06 and other originally-mil-based rounds, the PPC is shorter, larger-diameter, and longer-necked.

A few reasons, offered by its creators, why PPC shoots so well: One, it’s a short case, a scant 1.515 inches overall. That makes it more rigid and less susceptible to warp. It also means it fits into a short action, also more rigid (and with shorter bolt travel). The case neck is relatively long, which means the entire shank of the bullet is within the neck, never below it. That means no influence from varying cartridge wall thicknesses (the case neck walls can be made near-perfectly consistent), avoiding the case neck “donut” at the neck, shoulder juncture. Its body area diameter is 0.440-vicinity, which is (was) a good deal larger than the more common 0.378 commonly used in Benchrest. Case shoulder is 30-degrees.

About that: Well before the PPC there was P.O. Ackley. Well-known for his “Ackley Improved” rounds, which, pretty much, were standard rounds with a sharper shoulder angle. In sharpening (flattening) the shoulder angle (usually from 23-degrees to 30 or even 40), that also elevated the shoulder, and that increased case volume. More speed! Another benefit of the sharper shoulder was a notable reduction in the “flow” of the brass. That meant less change firing to firing. The sharper angle on the shoulder essentially “caps” the flow in that area.

ackley improved
Dang. These always look so radical, but it’s a proven formula: the Ackley Improved. My Dad used one of these in .270 decades ago (P.O hisseff built his rifle) for elk hunting. Shown is an AI 280 Rem. which nearly equals the power of 7mm Magnum.

Other attributes engineered into the PPC have and haven’t been incorporated into subsequent new cartridges. Notable is the smaller-than-standard flash hole. This requires a likewise smaller sizing die decapping pin. Also, PPC uses a small rifle primer, which is fitting based on its overall round size. Over years, there have been retro-engineered common rounds with small primer pockets and those have worked well. For a spell, over the time it was available, small-primer .308 Win. brass found great favor among competitive shooters. Remington made it. Interestingly (again from a perspective of one who isn’t an engineer) pressures were higher compared to standard loads based on routine large-primer brass. Velocities tended to be more consistent.

Another reason for PPC perfomance is one I don’t pretend to understand, and that is its “efficiency.” That’s all in the science of internal ballistics and I only can attest to its influence. I have been a PPC user (the 22 variant) for a good while. It’s what my main NRA High Power Match Rifle is chambered in (AR15 platform). From virtually the same amount of the same propellant, there’s a solid +100 fps gain over the .223 Rem. The structure of the PPC indeed “works.” From that, and from “those” (High Power shooters), rapidly evolved experimental takes on the essential PPC.

Moving on, rounds like 6BR and 6.5 Grendel are outgrowths of the PPC format (“upgrowths” actually: they’re bigger capacity). We’ve also seen the essential influence in the popular 6.5 Creedmoor and the 6XC, which currently dominate competitive across-the-course and long-range shooting (“standard” long range, not the 2-mile stuff, that would be .375 Cheytak…).

6.5 grendel
Cuzzin to PPC is 6.5 Grendel (left), which grew from earlier experiments by NRA High Power Rifle shooters in creating PPC “tall-boys.”

Looking at semi-auto developments, many of which have been coming at us fast and furious, it’s clear cartridge developers are exploiting these same ideas. There is a (short) limit on what will fit into an AR15 upper receiver, for instance, because, one, it’s a finite amount of space, of course, and, two, there’s a magazine box, and these are related. More power in this platform means a fat case.

Now. I am in no way suggesting anyone run out and tool up for PPC in the next rifle! It can be soundly beaten in the “real world” of our needs from a cartridge. There are similar rounds with more velocity, easier availability, lower cost, and on down the list of desirables. In the next couple of issues, I plan to talk more about some of the newest rounds, but wanted to offer just a little retrospect on where it all came from before getting into where it’s gone!

This article was adapted from content in Glen’s newest book: America’s Gun: The Practical AR15. Go check it out HERE

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

Check out AckleyImproved.com

RELOADERS CORNER: Improving Die Performance: 4 Simple Modifications

Facebooktwittergoogle_pluspinterestyoutube

Here are 4 low-to-no-cost setup tricks that will improve the concentricity of your loaded ammo. READ MORE

Glen Zediker

Cartridge cases and reloading dies all have centers. Trick is getting the centers to agree. When they do then that’s an asset to “concentricity,” and that’s attaining a major goal in the process of making better ammunition. A part that’s under pressure and moveable, such as a cartridge case being sized or a bullet being seated, moves toward a path of least resistance. If all associated tooling is “straight,” and the case itself is uniform, then the result is “straight.”

Accepting existence of tolerances and misalignments, taking steps to help two conflicting centers come close together comes from providing some free-play in the apparatus. I call it “floating,” and it serves to help, and here are a few ways.

To be clear: free-floating can help in two ways. One is to build-in float within the tool, and another is to create float and then use that to better center a tool. I’ll explain…

shellholder trick

1. Shellholder
Reloading presses with conventional shellholder arrangements use a spring clip to retain the shellholder in its slot. Remove it! It sits the shellholder off on an angle.

Get to a (real) hardware store and get an o-ring to secure the clip. The o-ring goes around the slot previously occupied by the clip. To install the shellholder just roll the ring down, slide in the holder, and the o-ring will pop back up to block  shellholder exit. Normally, the size needed is 7/8-inch outside diameter, 11/16 inside diameter, 3/32 thickness.

With the clip gone, the shellholder sits flat, as it should, and since the shellholder is free to move also allows some “wiggle room” so the cartridge case can center itself as it enters the die. This honestly makes a positive difference, especially in bullet seating, it seems.

NOTE: for these next “tricks,” choose a case that represents your “best,” one that’s got the most consistent neck wall thickness.

indexing dies on reloading press
Always put an index mark from die lock ring to die body to press top. That’s a simple way to verify return to “zero” when a die is installed back into your press. And ALWAYS install and remove the die holding ONLY the locking ring! Never the die body. Any bit of body rotation within the locking ring requires repeating the process of die adjustment.

2. Sizing die lock ring
Speaking of “wiggle room,” there’s just a little too much of that in a 7/8-14 thread. It’s pretty coarse. Taking up the play created by thread-to-thread gaps results in “straighter” die installation.

Always (always) secure a die body locking ring when there is a case inside the die, and with the ram in its fully upward position (press handle all the way down). This bit of pressure helps bring the die into better alignment. It also makes the die difficult to remove after snugging down the lock ring. Just get stout on it, and, after initial removal, subsequent re-fittings are easy. I use a “strap wrench” (plumbing supply and auto parts stores will have one). “Channel-Lock” pliers also work, but result in cosmetic, but not real, damage. Lock rings with wrench-flats are the bomb.

Before initial removal of the die after the snug-up step, draw an indexing mark from the die body to the die lock ring to the press top. That’s a simple way to return to “zero,” and also to know if anything got out of kilter. Use a paint marker.

3. Sizing button (expander) / decapping assembly
To get the sizing button in a sizing die holding on center, loosen the decapping stem lock nut and run a case fully up. Then slowly retract it until you feel the button enter and lodge into the case neck. Now. Put just a little pressure back in the “up” direction (down on the press handle) and then tighten the decapping stem lock ring.

This really makes a difference, by my notes.

adjust sizing die expander
When it’s possible, and it almost always is, secure the pieces-parts when they’re doing their jobs. For instance, tightening the locking rings on a decapping stem when the expander is holding inside the case neck helps bring the stem into straight alignment, and the expander along with it.

4. Bullet seater
Follow the same die-body-lock trick, after a bullet has been seated, and also just in the same as described for centering the sizing button (just keep the pressure “up” rather than retracting the handle) while you lock the seating stem. Flushing the die body makes a difference. Centering the seating stem may or may not, depending on the style of seating die you have. The “sleeve”-type seaters (like the Redding Competition) are already in alignment so the seating stem itself can’t be influenced. As said, the body can get a help.

index sizing die
O-ring trick: the flexible ring allows for some “wiggle room” to help case and die centers match. Trick is reinstalling the die to hold the desired setting, and the index mark really helps.

One more: Lock-ring o-rings
Here’s another trick I can suggest, but don’t really use… That’s because it, indeed “works,” but I prefer these other means. The trick: install an o-ring under the die body locking ring (for sizers and seaters). This allows some movement, positioning flexibility, in helping a case center as it’s entering the die.

If you do this one, most definitely index-mark the die ring to the die body and then the ring to the press top, as suggested. Never touch the die body itself to thread in or out the die. Hold only the lock ring! (And that’s true regardless.) O-ring size is 7/8-inch inside diameter and a thickness of 1/8-inch.

NOTE: My topics over the past few editions have tended be a tad amount “nostalgic,” and there’s some reason. I just finished a new book, and this one took me way on back to the start of when I discovered reloading, which coincided with discovering my first AR15. It’s called “America’s Gun: The Practical AR15.” It will be available here soon, but not just yet. But go take a look! Information is on my web site HERE. I’m really proud of it. 

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