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RELOADERS CORNER: Barrel Throat Erosion

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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: Standard Deviation

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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: Understanding Ballistic Coefficient

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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

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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

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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

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RELOADERS CORNER: 4 Firings In, Part Two

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Cartridge cases always fail on the “next firing.” Question is which one that might be. Need to know! KEEP READING

beat case
I apologize for the image quality, but these were taken a while ago. Fortunately, for me, I didn’t have anything on hand that shows even close to the beating this one took. Cracked neck, head crack. Rare to see one case with both of the most common failures. It was attacked by an M14.

Glen Zediker

I’d always rather say it all at once, but the realities of tolerance, and space, sometimes mean I have to split a bigger topic into smaller installments. The “tolerance” part is how many pages you all are willing to scroll through!

This multi-part topic is when, and then how, to check after the progress of changes commencing with the firing on a new case. It’s the “progress of degeneration,” in a way of looking at it because the concern is getting a handle on when enough change in the brass has come about to require attention. Or abandonment. As said then, for me that’s 4 firings. That, as said last time, is when I might see changes that need attention. Also as said, that figure didn’t come out of a hat, but from my own notes in running my competition NRA High Power Rifle loads.

The areas most affected are the case neck and case head area. Case neck walls get thicker, and that was the focus last time. Well, the case head area body walls get thinner. Primer pockets get shallower and larger diameter.

As started on: Brass flows during firing. It expands, then contracts, and when we resize the case, it contracts, then expands (a little). This expansion and contraction makes the alloy harder over the entire case, but with more effect in areas of more expansion, and flow. Replace “hard” with its effect, “brittle,” and that’s a clearer picture. This increasing hardness influences its reaction to being sized or otherwise stretched. As with many metals, bend it back and forth enough times and it will break. It will also fail if it loses enough resilience, or thickness, to withstand the pressures of firing.

Case Head
When a case is under pressure during firing, the brass, like water, flows where it can, where it’s more free to move. Of course, the chamber steel limits the amount it can expand. The case shoulder blows fully forward and the case base is slammed back against the bolt face. There is, therefore and in effect, a tug on both ends — it gets stretched. The shoulder area is relatively free to expand to conform to the chamber, but the other end, the case head area, is not. Since that’s the area of the case with the thickest walls, it doesn’t expand “out” much at all. What it does is stretch.

The “case head area,” as I refer to it here, is the portion of the case above the web, which is just above the taper that leads in to the extractor groove. The “area” extends approximately an eighth-inch up the case body.

case pressure ring
Here’s a “pressure ring.” You’ll see this after firing, if you see it. And, if you see it, that case is done. The bright ring indicates excessive stretching, which indicates excessive thinning.
head separation pic
Closer view of another sectioned case. This one here was fixin to pop. 

That portion of the case does not fully expand and grip the chamber, but the area immediately ahead of it does. So the case body expands and grips the chamber, and that last little bit back to the base can and does move. It stretches. If you see a ring circling the case, noticeable because it’s lighter color than the case body, and it’s in this area, I’d say that case is done. The ring will be evident after firing, not after; don’t confuse a shiny ring around the case in this area with what can be normal from sizing, especially if it’s been a hotter load. That is pretty much a scuff from the sizing die squeezing down this expanded area.

And that’s right where a “head separation” occurs. It can crack and also blow slap in two, and that’s the “separation” part of case head separation.

This is a spot to keep close watch on as cases age. It is also the area that is more “protected” by sizing with less case shoulder set-back. That is, pretty much, where the freedom for the stretching movement in this area comes from (the case shoulder creates a gap). However! As said many a time, semi-autos need some shoulder set back for function, and it’s the reason to use an accurate gage to determine the amount of set-back needed.

case head separation
Ultra-high-precision gage, made by me. Not really. It’s a selectively bent paper clip, and running this down inside the case and and then back up the case wall can signal a dip-in in the head area, which signals thinned walls. Feel it? Case is done.

Some folks unbend a paper clip and run it down inside a case and drag it up against the inside case wall as a sort of antenna to see if they detect a dip-in near the head area, which would indicate that the wall in this area has been stretched thinner. If there’s enough to feel it, that case is done.

Since I’m working off this “4 Firings In” checklist, if you’re seeing a sign that a head separation might be nigh in that few uses, chances are the shoulder set-back is excessive, and also too may be the load pressure level.

Primer Pocket
Another case-head-area and pressure-related check is the primer pocket. As said, the primer pocket will get larger in diameter and shallower in depth each firing. As with many such things, the questions are “when” and “how much,” and the main thing, “how much?”

If the pocket gets excessively shallow, and that’s judged by a primer that seats fully but isn’t at least a tick below flush with the case base, there could be function issues. There’s a risk of a “slam-fire” with a semi-auto that uses a floating firing pin, and, if there is actual protrusion, that has the same effect as insufficient headspace.

primer pocket uniformer
A primer pocket uniformer can reset the depth of a shallowed primer pocket to what it should be, but the real test for me is how easily the next primer seats into it. If it’s significantly less resistance, I’ll say that case is done.

Shallower can be refurbished. That’s a primary function of a primer pocket uniformer. Larger diameter, though, can’t be fixed. I’ve mentioned in another article or two that, any more at least, my main gauge of load pressure has become how much primer pocket expansion there’s been. I judge that without using the first gage, well, unless my primer seater is a gage. If a primer seats noticeably easier, that’s the clear clue that the pocket is too big. Another is seeing a dark ring around a fired primer, indicating a little gas leakage.

Measuring primer pockets is a waste of time, say my notes at least. First, it’s not easy to accurately (truly accurately) measure a pocket, especially its diameter, but, that’s not really what matters. It’s how much grip there is to maintain the primer in place during firing.

I pay close attention to resistance in primer seating and won’t reuse a case that’s too easy.

Good deal on what I think is good brass, especially if you’re an AR15 loader — 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

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

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RELOADERS CORNER: 4 Firings In

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Along with all the other operations we do to them, cartridge cases also need maintenance. A good question is “when”? That’s next… KEEP READING

old case

Glen Zediker

I tend to write much of what I do for those who reload for production. Those are folks expecting good utility in exchange for the expense and effort: a reliably-performing round of ammunition, over and over again. They’re loading and reloading because they like to shoot. It’s a big bonus to most, and I include myself in this group most of the time, if that good performance comes with a minimum of effort. Clean, size, prime, fill, seat, shoot. Five steps to get to the one thing that matters most: shoot! I am also in another group some of the time, not as often now as I once was, and those folks may add a few more steps before getting to the “shoot” part (case prep mostly).

It would be wonderful if that simple cycle endured without end. But it won’t.

Overall case condition after X-many firings varies A LOT because of a lot of factors, variables. What matters is getting a handle on it. I look over each case each time I load it, but I don’t break out the measuring tools. That’s not neglect. There is never (ever) any excuse for neglect. That’s not what this is about. It’s about working out a responsible, reasonable, and realistic schedule for when to take a close look at the progress in condition that new batch of cartridges cases has followed after some time.

In my experience, which is what’s in my notes, I say that’s 4 firings.

I went through the per-use checks enough times to know the schedule one brand and lot of brass, used with the same loads in the same barrel, follows with respect to changes. And by that I mean when changes require attention. I’m also starting with prepped cases, including trimming, before their first firing.

Let me make clear that I’m not suggesting that 4 firings is maximum case life! What I am suggesting is that this is the point where it’s likely to see measurable influences from use and reuse, and, as such, that it can be measured. That’s what we’re after now: take a check to see what’s happening, and that also is a big help toward getting clues about where and when these changes might get noticeably influential.

So, to be clear: the case has been fired four times, reused three times. Next loading, if there will be one, will be for the fifth use.

chamber reamer
We, or more correctly, our cases, are at the mercy of this thing: a chamber reamer. It sets the amount of space the case can expand into.

Changes
Continuing to use and reuse cases, we’re not really using the same cases each time. The cases change, and much of the change comes from material flow, which is brass.

Here’s how it goes, which is to say here’s how it flows: Case neck walls get thicker. The case head area body walls get thinner, over a short span of the body. Primer pockets get shallower and larger diameter. Overall, the alloy hardens over the whole case.

As gone on about a few times in this spot, there’s going to be more change in cases run through a semi-auto than those used in a bolt-action. That’s because of the necessarily additional (comparatively speaking) sizing and also the additional stress resulting from the firing cycle. There’s more flow because the cases are free to expand more.

drop bullet
A simple, and important, test to check if case necks walls have thickened excessively is to take a fired case and drop a bullet in it. If it won’t drop without resistance, stop! That’s way too much.

The Neck
All case necks expand to whatever the chamber allows. There’s no relationship between that and sized dimension because, clearly, there has to be a small enough neck inside diameter to retain the bullet. It is, though, one of the reasons case necks tend to give up quickest (plus it’s the thinnest-walled area on a case).

The case neck is my primary concern, and the first thing I check. If the walls get too thick it’s possible to cut the space too close between the case neck and the case neck area in the rifle chamber. There might be interference upon bullet release, and that creates excessive pressure, or sure can. All that depends on what the chamber allows for expansion room.

The most simple check is to see if a bullet will freely drop into a fired case neck. If it won’t, stop! Do not reuse that case as-is. A case that won’t pass this no-tool test has excessively thickened.

Somewhere in your notes should be a figure indicating loaded outside case neck diameter, on new brass. This dimension is exclusive of the sized neck diameter, because when the bullet is seated the neck is going to expand to accommodate the bullet. Another check of loaded outside neck diameter will show if there’s been thickening. If an inside neck sizing appliance is used (a sizing button), then that will tell you also, comparing it to what you also recorded for the new case after sizing it. (And it’s a good reason to always run new brass through your sizing die, even if it’s “ready to go” out of the box.)

I hope it’s clear enough why it’s important to “write everything down.” References, standards are big helps.

Direct checks of the neck walls themselves using a suitable tool will show thickening. However! Case necks don’t necessarily thicken the same over the entire height of the case neck cylinder. Remember, the brass is flowing so moves in a direction, and that part of the case has a wave going forward, toward the muzzle. There can and likely will be a tapering from thicker to thinner. Measure at more than one point.

Safety is one thing, and the most important thing, and then the other thing is accuracy. Case neck “tension” needs to be consistent from loading to loading to get reliable accuracy.

Fixing it? An inside case neck reamer is the easiest and most direct means. However! Make double-dang sure you know the numbers and therefore how and at what point to use it! Many are intended for use on fired (not yet resized) necks. Others are a specific dimension that you may or may not be able to specify. Thinning the case neck walls using an outside case neck turner is another direct remedy. A little tedious.

forster reamer
The best way I know to remove material to refurbish overly-thickened case neck walls is an inside case neck reamer. This is a Forster, designed to work with their case trimming base. Trick is knowing the case condition it was designed to be used with. This one is dimensioned for use on fired, unsized case necks (it’s 0.003 under bullet diameter). Run it on a sized neck and way too much brass comes off. Various sizes are available.

Reamer or turner, though, this job hasn’t finished until the refurbished case has been run through your usual sizing die, and checked again for diameter.

Well, so much for this here and now. Out of room! More next time…

See REAMERS 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

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

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RELOADERS CORNER: Choosing Your Brass

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It’s not all the same! Depending on needs and application, there are three decisions that can have an impact on your satisfaction. READ MORE

norma brass

Glen Zediker

Last time I offered a few ideas on loading the same cartridge for use in different rifles. Essential message in that was, in one word, “compromise.” There’s some give and take when we’re trying to please more than one at time, as such is life…

Choosing cartridge cases is a little, to a lot, the same. Different rifles, different action types, different uses, different budgets, all suggest input that helps determine what works best, all around.

There are three things to consider, maybe four.

One is the action type. Semi-autos need “tougher” brass. That, overall, means “harder,” not necessarily thicker. Due to the resizing requirements for good function, which means a little “more” in all areas, there’s likewise more expansion in each subsequent firing. Brass made of harder alloy is less, not more, susceptible to failures — by my experience. Considering the elastic and plastic properties of brass, harder exhibits a little less effect from each.

I prefer harder composition brass for a bolt-gun too. Most NRA High Power shooters do. Reason? It runs better! There’s less “stickiness” in running the bolt for rapid-fire events.

Two: case capacity. They are not nearly all the same! My experience has shown me that more capacity is better, and that’s especially if we’re wanting to edge toward max-pressure loads. Even though the pressure generated inside the case using more (larger case volume) or less (smaller volume) may get to the same level, there is usually more net velocity (at the same pressure) when there’s more room in the case. If it didn’t matter then other things done to expand case capacity (like shoulder angle changes) wouldn’t matter either.

cartridge case capacities
Case capacities vary, and, as you can see, a good deal. These .223 Rem. are each filled with an equal amount of spherical propellant.

Three: Precision standards. What do you expect, what are you willing to do to get it? After enough experience with enough different brands, that is a legit question. Some brass is “better” out of the box. Cost usually reflects on initial quality. Paying a premium for premium quality, which is three things: consistency, consistency, and consistency. That consistency will primarily, or at least measurably, be in wall thicknesses. The choice there is to buy it or make it. That choice is a balance between effort, value of time, and proven results.

lapua brass
Consider first-use or re-use? Good stuff! And you’ll pay for it! Lapua cuts case prep down to sizing: the case heads are milled, the primer pockets and flash hole are reamed. It’s also a little thick and a little soft. Single-shot-style use in a bolt-action, can’t really beat it, but my AR15 Service Rifle beats it to death.

After using enough different brands with varying levels of costs and claims, I think the most honest thing I can tell you is that you’ll likely end up with the overall “best” brass case you can have shopping in the middle, plus a little, and then getting to work on it. A good commercial “name” brand can be made at least effectively close to the dimensional equivalent of a premium brand, like Norma, but it’s not without effort.

Before spending any time weighing or otherwise sorting cases, do all the prep work you plan beforehand. If any prep involves material removal, even trimming, that influences weight accuracy and, therefore, the viability of segregation by same.

Recommendations?
Yes. And no.

About the time you decide there’s some certain way some certain thing is, they up and change it. I avoid making too many lumped-together, generalized statements about particular brands because of that. However! I can tell you that some of the “better” brands of brass also tend not to hold up as well, or won’t if there’s much working load to load (expansion, sizing). I’m thinking here of the better-known European brands, like Norma and Laupua. Those are near about dimensionally flawless out of the box, but they tend to be a little on the thick and soft side. I use Norma in my .22 PPC because the cost is worth it. If I drive from Mississippi to New Mexico to shoot a match, that’s the least of my expense.

nosler brass
This isn’t cheap either, but I have had good results with it. Nosler is, or can be, ready to go out of the box, including case mouth chamfer. It’s held up well for me in semi-autos.

This is also the reason that every serious competitive shooter I know says to buy up as much of one lot as you can, if you know it’s good stuff. That’s for all components.

Sometimes brass chooses you!

As said last time on the “Multiple Gun” loads, if you’re mixing brass things like case volume do factor. As also suggested then, the best solution is to pick a load that’s in around the 80- to 90-percent range of max. I mix brass all the time. I shoot quite a lot of factory ammo and, yes, I save each case we can retrieve. I clean them all, size them all, and fill them with a “compromise” load I worked up for can blasting. The need for those excursions is not quarter-minute precision.

If you’re looking to save as much as you reasonably can and still get “good” cases there’s honestly nothing wrong with Lake City. The more recent production 5.56 measures pretty well, and it’s tough, and relatively high-capacity. I sho can’t vouch for any other headstamp on mil-spec ammo beyond “LC.” However! I suggest purchasing it prepped. Avoid “range dump.” A big issue with once-fired is which chamber it was first-fired in. Avoid .308 Win. (7.62 NATO)! You DO NOT want to deal with M60 or Minigun leftovers.

lc nm brass
This is LC Match 7.62. No primer crimp! For reuse in a semi-auto, it has the right stuff, which means made of the right stuff: it’s hard, tough.

Start HERE on Midsouth. Great deals! Great brass!

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

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RELOADERS CORNER: Fire-forming

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New cases? Decisions you make before that first firing have a lot to do with future success. Read why (and how) HERE

Glen Zediker

case segregate
I segregate my new cases before firing because I need to know which are for which. Do not first-fire cases using a lighter (less pressure) load unless you intend to continue to use that load in those cases for subsequent firings! I’ll use “old” 300- and 600-yard cases for offhand practice, but never the other way around!

The past few articles I’ve been begging indulgence from all the bolt-gunners out there by focusing on a few semi-auto-based topics, and so this time I’ll get to something of more interest to them (and it’s also of interest to “all of us”). In practical terms, which is living with reloads, it is at least of as much interest, or at least importance, to someone running an AR15 (if they’re looking to get maximum on-target performance from it). Subsequent case life has a lot to do with how you go about firing that first time.

So: definition: “Fire-forming” is a term usually associated with describing changing a cartridge from its original or “parent” state into another state, which is a non-standard cartridge, when it’s first-fired in the non-standard chamber. Like making an Ackley-Improved version of a standard cartridge, or converting a .250 Savage into a 6XC. In other words, the firing itself expands and reforms the case to the shape of the new chamber, and the case that emerges is then the new cartridge.

But! All cases are fire-formed to the chamber they’re first-fired in.

Details: Brass alloy is both plastic and elastic. That’s the “technical” reason changes in a fired case can and does occur in the first place. Plastic means that brass can expand and flow to fit the chamber, and retain its new shape. Elastic means that it doesn’t fully and completely mold itself to become a new mirror of the chamber. It “snaps back,” retracts from its maximum expanded form. If it didn’t it wouldn’t want to come back out of the chamber. That “snap-back” amount is predictably 0.001 inches.

case mushroom
Here’s a good example of the plastic property of brass alloy. This is a .250 Savage case that’s been run through a 6XC sizing die. Next step is to load it up and fire it in the 6XC chamber. It comes back out looking just fine! By the way, the little dings and creases we see in spent cases sometimes are really nothing to worry about: they’ll iron out after firing again.

On any rifle with a “standard”-dimension chamber, a new brass cartridge case will be smaller than the chamber. Has to be. It wouldn’t fit if it weren’t. A “standard” chamber, here, means there may and likely will be small variations from chamber to chamber (reamers vary uniquely, as might the operator’s preferences and judgment regarding how “tight” the headspace will be), but nothing intentionally has been done differently to alter the chamber beyond SAAMI-spec dimensional tolerances. Anyone who has loaded for the same cartridge for more than one rifle, and who has recorded pre- and post-fired case dimensions, knows that it’s common for there to be at least a thousandth or two, or more, variance. That’s all fine, as long as it’s within spec. Some custom-done barrels might have a chamber that’s intentionally different than SAAMI blueprints, and that’s a whole different topic.

Back to it: Since the brand-new cartridge case is smaller than the chamber it’s going into, it’s going to expand, grow. That’s clear.

ppc tallboy
Here’s a .22 PPC (left) next to a wildcat version, the “Tallboy.” There’s a whopping lot of permanent stretch to make this round (which is the precursor to 6.5 Grendel by the way). It is really important that this initial firing be done with a stout propellant charge. They would, not may, fail if the first firing didn’t fully expand the shorter PPC case.

So, there are two “forms” fire-forming can take. As said, no matter what else, all cases are formed to the chamber on their first firing. However, for some there can be some benefit from approaching that initial firing following a method or means to establish the set-in behavior of that case on subsequent firings and reloadings.

Here’s why some planning and procedure matters: Brass alloy has a “memory.” This is, more technically, called a “shape-memory effect,” and is shared by some other alloys also. It expands (and contracts) in a consistent pattern each use.

The first firing establishes that pattern. On subsequent firings, less is okay, but more is not. Lemmeesplain: I strongly recommend first-firing with a stout load, or at the least the stoutest load you plan on running through that case in future uses. When I segregate my new cases, I’m sorting them based on their function for me. My best go to the “600-yard” pile, then to 300 and then to short-line. Those are three different loads. I need to know which cases are for which before I make the initial loading. Fire-forming with a lighter load and then using a nearer-to-max load in that same case will, not can, result in premature failures in that case. It doesn’t seem to matter much going the other direction. I would never charge up my 600-yard load in a case formed using my 200-yard load; there are significant pressure differences in those two.

If it’s necessary to reform through firing, making a new cartridge case, there are a few different methods I’ve seen used, but, what really matters is that the case fully forms to the new chamber. The usual influential changes occur in the case neck and shoulder, and also stretching fore and aft. The bigger the change the more important it is to fire initially with a full-power load. For maximum effect, it’s better to fire-form with something closer to a “max” load than something lighter. Brass gets harder each use, less pliable. Starting life as a new cartridge after that first firing, case life is longer, and better, if the case was fully formed.

dead length seating
For maximum subsequent case life, it’s important that, one, a case fully forms to the chamber. But! Two, also that needless stretching is avoided. To that end, first-firing with the bullet seated to touch the lands minimizes stretch. Reduce the load since this will, not may, raise pressure.

To aid that, a “trick” that helps a lot is to seat the bullet into the lands, firmly. The reason is because that already has the base of the case firmly seated against the bolt face. That prevents the primer strike from moving the case forward, resulting then in additional body stretching (beyond what already might be necessary). If it’s not the routine means used for bullet seating, this tactic requires a reduction in the load. When a bullet is moved from “just off” to “just on” the lands, pressure spikes at least equal to the value of 0.2-0.3 grains of propellant.

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

RELOADERS CORNER: Life in the Fast Lane

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Here are a few tips for getting the most, the easiest, from high-velocity semi-auto .224s. READ IT ALL

22 nosler

Glen Zediker

Here’s the conclusion of my “trilogy” on the movement of .224-caliber rounds into the left lane of rifle cartridge choices. The focus last time was on the 22 Nosler and .224 Valkyrie, and here are some ideas on making the most from either, or another similar.

First: Getting high (higher) velocity is really not rocket surgery: make the bullet smaller and the case bigger. Rounds like .243 Win. showed that clearly. However!

Speed, greed, need, (and heed)
Higher and higher velocities bring about a “debate.”

After messing with all this for decades, there are two things I know for sure about bullet velocity: more velocity shoots better; more velocity shoots worse. But! It’s not velocity itself. It’s a common belief, and totally plain wrong (and wrong-headed), that lower-velocity shoots better groups. It’s also wrong that higher velocity shoots better groups. Working with one cartridge and one bullet, for example, I’ve had plenty of times when the faster the bullet went the better it shot, and the slower the bullet went the better it shot. That’s all to do with the “combination” of the propellant and bullet and barrel and son on and on and on. Point is: it’s way on better to find a combination that shoots better and better the faster the bullet goes. That didn’t have a lot to do with the point of this, but it is important to keep in mind — velocity is not evil.

I know I don’t have to go into benefits of higher velocity. Hard to argue with those. What I do want to go into is a look at how much more and at what cost. Virtually every downrange improvement has some sort of cost. The cost of higher velocity is barrel life, mostly.

As said, higher velocity comes from more propellant. More propellant produces more flame and more gas. There’s a term, “overbore,” that gets around in discussions of, usually, large cartridges, like magnums. It actually is a mathematical device that compares the barrel bore area to the cartridge case volume. It is “V” (case volume) over (divided by) “A” (barrel bore area) and the answer, “O,” is therefore a ratio. The bigger O gets the more overbore the combination is. Applying that, something like .243 Win. is overbore. That’s also why a barrel chambered in that round lasts no more than 1200 rounds at true peak accuracy. That round is not considered overly powerful by anyone I know, yet, has the same sort of (bad) effect on barrels as does something like a .300 Win. Mag.

As said last article: clearly, barrel life in Nos. or Valkyrie is going to substantially shorter compared to .223 Rem.

Suggested Mods
Higher and higher velocities also come from varying propellant choice. Specifically, slower-burning propellants literally fit better into higher-capacity cases. Recollecting back on something I’ve mentioned umpteen times in these pages: propellant burning rate has a whopping lot to do with semi-auto manners. Slower-burning propellants elevate gas port pressure, which brings on the “over-function” symptoms, none of which are good. There’s a comparison of 22 Nosler with .22-250. They’re similar in structure. General consensus is that a favored propellant in the .22-250 is H-380 (if you don’t like that one, and I don’t, it’s going to be another in that burning-rate range). So. Point: 22 Nos. and Valkyrie do not get the most they can get from a “safe” .223 Rem. propellant (I break that off at nothing slower than H-4895). For good instance, I run Varget in my Nos. and that’s the same propellant I run in my PPC. It’s a little too slow, my opinion, for a stock gas system in an AR15.

Most running a 22 Nosler or .224 Valkyrie are looking to exploit speed, so will, therefore, be shopping or specifying 24-inch barrels (that’s a “standard” available length). That, combined with a standard 12-inch “rifle” gas port location, will, not can, escalate pressure within the gas system. That combination also puts a .223 Rem. over-pressure. (Reason is that the post-port length add increases “dwell-time,” which is the duration that the gas system is containing maximum pressure.) The best solution to excessive port pressure is to move the gas port! “We” (competitive High Power Rifle shooters) have been doing that for better than 20 years.

Yardstick: Plus-1-inch for .223 Rem. and plus-2-inches for Nos or Valkyrie. That makes a huge difference! Of course, this mod is only possible if you’re going with a custom barreling op done by a competent and savvy builder.

long gas tube
More gas and a longer barrel team up to over-charge the gas system. The best initial solution is to get your barreler to move the gas port forward (which means custom parts). No step for a stepper! Custom tube shown with standard rifle-length (top).

Without that, there are two options that, I say, should be used in tandem: a valved gas block and increase buffer/spring mass and resistance. The adjustable block reduces the amount gas that gets into and is contained within the system and the other offsets the effects of the harder hit the bolt carrier group will be subject to.

odin adjustable gas block
An adjustable gas block will, indeed, work to reduce excess gas pressure. There’s going to be erosion in the mechanism, though, so over time it’s going to change in its function. My personal favorite is the Odin Works, and one reason is that it’s rebuildable.

odin adjustable gas block

I am a bigger fan of the “architectural” solution rather than the adjustable gas block. They won’t last forever…

Another important spec I want to hit on: barrel twist rate. As said last time, the .224 Valkyrie was, so they say, designed to handle the biggest of the high-bc .224 bullets and, specifically, the Sierra 90 MatchKing (and similar). That’s why, as also said last time, commonly offered twist rate with that chambering is 1-7. Folks, 1-7 isn’t enough, in my experience, for 90+ .224 bullets. I (“we”) use 1-6.5 twist for 90s and the others in 20-inch barreled Service Rifles (.223 Rem.). That’s quick. Those shoot 77gr “magazine” bullets really well also. With Sierra now offering a 95gr .224, go with a 6.5. The extra velocity from Valkyrie and 22 Nos does indeed boost rotation, but I strongly suggest not relying on that promise for stability. It’s edgy.

sierra 95 SMK
Dang. An SMK 95gr .224… 27-caliber ogive! Best get some spin on this bad boy. I recommend a 1-6.5. Experience has been that 1-7 is borderline adequate for any bullet in this length range, and I’m not a fan of borderline, or “adequate.”

1-6, by the way, tends to blow up bullets.

valkyrie nos chart

The preceding is a specially-adapted excerpt from Glen’s newest book, America’s Gun: The Practical AR15. Check it out HERE

LINKS

SMK 95

Adjustable Gas Block

Some (not all) sources for fast-twist barrels
(I’ve used these in happiness)
Pac-Nor
Krieger

Check out components at Midsouth HERE for Valkyrie and HERE for 22 Nosler.

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