Tag Archives: case sizing

RELOADERS CORNER: Semi-Auto or Bolt-Action? Two Things To Remember

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There are essential differences in loading for these action-types. It might not matter if you know all about the one, but it is critically important to know about the other. Find out which is which… Keep reading!

casing in air
Any rifle with a gas operation system has to, well, have gas to operate! When it gets excessive is when the problems start. That’s another article, but the effects of the operating system is the basis for both the cautions in this article.

By Glen Zediker

Over the time I’ve been producing Reloaders Corner here at Midsouth, my focus has been exclusively on reloading for rifles, and, within that, primarily for semi-automatics. The reasons for that are based on two things, one is an assumption and the other is plain old fact. First, semi-autos are popular and represent the interest of a great number of new reloaders out there, and that’s my assumption. It doesn’t take long to come to the conclusion that high-capacity magazines and long days at the range combine to get expensive in a hurry! But the biggest reason I focus most of my material toward the needs of the semi-automatic rifle is because there are decidedly important differences in some decisions the handloader makes when tooling up for one. That’s the fact. Not knowing or respecting these differences can be disastrous.

I set out to be a sticker for clarity, but sometimes I overlook making more pointed references to these differences, when there are options associated with any one topic. I judge that based on the feedback I get from you all respecting tooling and component options. I want to start the New Year with this article, which I think contains some basic and important information to always (always) keep in mind. Hopefully it will also reduce questions, and I sure hope confusions. It also seemed to be, judging on feedback, the topic that created the most questions and comments.

Essential: When a round fires, the case expands, in all directions, as much as it can to fit the chamber. Since brass is elastic (can expand and contract) and plastic (can expand and retain that expansion) that last attribute, plasticity, results in a spent case that’s closer to rifle chamber dimensions than it was to its factory-new figures. Since many factory barrels have relatively generous chambers compared to most custom-done barrels, that’s either good or bad, depending on whether it’s a semi- or bolt-gun, and also depending (a lot) on what anyone buys into.

So, for reuse in a semi, that now overly-dimensioned case has to be brought back closer to nearer-to-new condition than it does for a bolt-gun. Has to be. Otherwise it might not chamber smoothly or fully.

full length sizing die
Due to the greater amount of case expasion, and also due to the need for smooth, easy feeding, any and every case used for a semi-auto should be full-length resized.

It’s important to understand that any semi-auto (at least any I’ve yet had experience with) has the cartridge case in a different condition right at the start of the extraction cycle. In a semi, the case is still holding pressure when the bolt starts to unlock. Bolt-gun, it’s all long gone by the time the knob gets lifted. That’s why a freshly spent case from a semi will raise a blister and one from a bolt-gun is cool to the touch. This pressure creates what amounts to greater case expansion in a semi-auto. Depending on the particular rifle and other factors that will get addressed in other articles, this varies from a little to a lot. The spent case measurements from one fired in a semi may not accurately reflect chamber dimensions, as they will with a bolt-gun.

The reason there’s still some pressure within the case when the bolt starts to unlock is because that’s how a gas-operation system functions. If all the pressure was gone the action wouldn’t even open.

neck only case sizing
A bolt-gun can be neck-only sized. I honestly don’t think this is a worthwhile practice, and I’ll talk more about that in another article, but as long as you’re willing to get a handle on case dimensions (so you know it’s still within specs to fit your chamber) it’s perfectly safe, and usually results in good group sizes.

Which brings us to the second essential difference in bolt- and semi-: Most semi-automatics, especially what is probably the most common (AR15 family) is very sensitive to gas port pressure. Gas port pressure is an actual measurement, but that’s not important to know, not really. What matters is understanding the effect of too much port pressure, and that is too much gas getting into the operating system, and getting in too quickly. That creates what most call an “over-function.” The action tries to operate, and the extraction cycle starts too early. There’s a lot of gas still binding the inflated case against the chamber walls. Many ills: excessive case expansion, excessive bolt carrier velocity, extraction failures (extractor either slips off or yanks the case rim, which can come off in a chunk).

.223 recommended components
Semi-autos are way on more sensitive about propellants, and, specifically, the propellant burning rate. Here is the set I use for my .223 Rem. competition loads (aside from a propellent that’s running in the range of the H4895, tough cases and thicker-skinned primers are part of the picture too).

From a reloading perspective, regulating gas port pressure is all in propellant selection. The burning rate range that’s suitable for semi-autos varies with the cartridge, but for both .308 Win. and .223 Rem. I cut it off at the Hodgdon Varget, Alliant RE-15 range: those are fine, but don’t go slower! Bolt guns don’t care about any of that.

RE15
Some will (certainly) disagree, but this is about the slowest-burning propellant I would suggest for .223 Rem. As a bonus, it’s also one of the highest-performing.

THE SHORT COURSE: Think “smaller” and “faster” when tooling up for sizing and choosing propellants for use (really, re-use) in a semi-auto. Smaller case sizing, faster-burning propellants.

This will all be hit on in upcoming articles in far greater detail but…

SEMI-AUTO: full-length case sizing, case shoulder set back at least 0.002 (from what a gage indicates as the fired case dimension), case neck “tension” at least 0.003 (difference between sized case neck outside dimension and loaded case neck outside dimension). Propellant selection: not too slow! Contrary to what logic might suggest, slower-burning propellants produce higher gas port pressures because they “peak” farther down the barrel.

BOLT-GUN: neck-only case sizing is (usually) okay (that means no case body sizing). Case shoulder set back: can be fine-tuned based on what’s necessary to easily close the bolt (ranges from none to “just a tad”). Propellant: doesn’t matter! As long, of course, as it’s suitable for use in that cartridge.

Check out some tools HERE at Midsouth

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

Reloaders Corner: Accuracy 2

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Accuracy matters! Now here’s what matters to accuracy… This article discusses 5 essential steps that pay off big.

Glen Zediker

Last time I wrote a little “essay” on the importance of accuracy and a few ideas on why it matters and how to judge it. That’s all well and good, but the part I knowingly left out was to say more about “how” to get the most of it. Here’s a few points that, over a many-many years, have proven themselves to me to improve the quality of on-target perforations, and, to make sure I’m clear, that is manifested by smaller-diameter shot groups. There are a plenty of others who agree with these tips. There are plenty of others who might not agree with all of it, and even a few more who would love to add their own “can’t miss” components to this mix. But here are mine.

concentricity

ONE: After-the-fact concentricity. By that I mean actually checking loaded rounds on a runout indicator. Concentricity is pretty much the goal for sizing, seating, and neck-related case-prep steps, like outside case neck turning. However! All those things are done to help support concentricity, but not a one of them is concentricity.

Concentricty is the centered relationship of all influential circles in a cartridge case, with the reason that a more concentric round will have its bullet looking down dead center into the rifle bore: ultimately, if the loaded round spins “flat-line” it will shoot better than those that don’t.

It starts with brass selection and then likely also segregation. Then it moves on to the quality of tool alignment.

I have checked enough factory-loaded rounds though a concentricity fixture, and those that show the best group the best; even if the overall group from random selections is so-so, “flatliners” shoot smaller.

Check out Midsouth products HERE

TWO: Inside flash hole deburring. I know I’ve mentioned this before, but this simple and easy step shows up on target next firing on thusly-prepped cases. It improves propellant ignition consistency and, depending on the tool used, also ignition efficiency.

Inside deburring tool
How and why an inside flash hole deburring tool works is pretty clear to see. Despite the fears I’ve heard, it will not hurt the integrity of the case.

There’s a burr inside most cases that resulted from manufacture (with only a few drill-cut exceptions, like Lapua, cartridge case manufacturers punch the flash hole). This burr is variable in size and scope, but it acts as a block to the spread of primer flash, and it’s redirecting or misdirecting the flash at the same time.

It only has to be done once. Ever.

Check out Midsouth products HERE

THREE: Primer pocket uniforming. This helps because it lets you set each primer the same, and also fully. The reason is that it squares the “edges” or corners of what otherwise is a slightly bowl-shaped cylinder. A perfectly seated primer is sitting square and flush on the bottom of the pocket, with its anvil legs compressed. This “loads” the compound for rapid and consistent ignition. If the primer isn’t seated fully then the firing pin finishes that job before detonation. That creates what equate to time variables — inefficiency.

Funny, but clean primer pockets don’t shoot any better than dirty pockets. What matters is flat pockets.

Check out Midsouth products HERE

FOUR: Consistent case sizing. There is a widespread fear, especially among some “accuracy” fanatics, about sizing ops. There’s also a lot misunderstood about full-length sizing versus neck-only sizing and so on. But. What matters is that, whichever tooling and how much sizing the cases are treated to, it needs to produce dead-same cases. Consistent case expansion dynamics is not often talked about, but it’s influential, especially on longer-range rounds. Just in general, going a little on the “light” side with sizing might seem like a good idea (less stress, less working the metal, etc.) but it can also lead to round-to-round inconsistencies. My belief is that it’s better to be more “positive” in sizing ops, and by that I mean to reduce a case neck 0.003 inches rather than 0.001 prior to seating a bullet. Get all the case shoulders the same height. Running extra-light case neck tension and leaving case shoulders where they emerged last firing may not reproduce round-to-round consistency, unless the rifle chamber was perfect and the cases were too. A little more sizing works the best for the most of us in the most rifles.

Forster seating die

FIVE: Invest in a good seating die. No doubt: the bullet seating operation is the “last thing” that happens and it’s also the one thing that can corrupt the care and treatment given to the quality of the loaded round prior. A sleeve-style seater, well machined, goes a whopping long ways toward preserving alignment, and, therefore, concentricity. Also make sure that the stem in yours comes to rest well down onto the bullet ogive, and, above all else, is not contacting the bullet tip! That will wreck a round.

seating stem
Remove the seating stem and drop a bullet into it. The farther down the ogive or nosecone the step recess grips the bullet, the better. If it’s only pressing down against the bullet tip, a crooked seat is assured, along with inconsistent seating depth.

Check out Midsouth products HERE

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